You know the mean of Khan?

 Khan  is a title for a sovereign or a military ruler, used by Mongolians  living to the north of China. Khan has equivalent meanings such as  "commander", "leader", or "ruler", "king" and "chief". As of 2015 khans exist in South Asia, Middle East, Central Asia, Eastern Europe and Turkey. The female alternatives are Khatun and Khanum. These titles or names are sometimes written as Han, Kan, Hakan, Hanum, or Hatun (in Turkey) and as "xan", "xanım" (in Azerbaijan), and medieval Turkic tribes. 

 "Khan" also occurs as a title in the Xianbei confederation for their chief between 283 and 289. The Rourans may have been the first people who used the titles khagan and khan for their emperors. However, Alexander Vovin (2007) believes that the term qaγan originated among the Yeniseian-speaking Xiongnu people, and then diffused across language families. Subsequently, the Göktürks adopted the title and brought it to the rest of Asia. In the middle of the sixth century the Iranians knew of a "Kagan – King of the Turks".[1] Various Mongolic and Turkic peoples from Central Asia gave the title new prominence after period of the Mongol Empire (1206–1368) in the Old World and later brought the title "khan" into Northern Asia, where locals later adopted it. Khagan is rendered[by whom?] as Khan of Khans. It was the title of Chinese Emperor Emperor Taizong of Tang (Heavenly Khagan, reigned 626 to 649), and also the title of Genghis Khan and of the persons selected to rule the Mongol Empire. For instance Möngke Khan (reigned 1251-1259) and Ogedei Khan (reigned 1229-1241) would be "Khagans" but not Chagatai Khan, who was not proclaimed ruler of the Mongol Empire by the kurultai. 

 Originally khans headed only relatively minor tribal entities,  generally in or near the vast Mongolian and North Chinese steppe, the  scene of an almost endless procession of nomadic people riding out into  the history of the neighbouring sedentary regions. Some managed to  establish principalities of some importance for a while, as their  military might repeatedly proved a serious threat to such empires as  China and kingdoms in Central Asia.[citation needed][tone] One of the earliest notable examples of such principalities in Europe was Danube Bulgaria (presumably also Old Great Bulgaria), ruled by a khan or a kan  at least from the 7th to the 9th century. It should be noted that the  title "khan" is not attested directly in inscriptions and texts  referring to Bulgar rulers – the only similar title found so far, Kanasubigi, has been found solely in the inscriptions of three consecutive Bulgarian rulers, namely Krum, Omurtag and Malamir  (a grandfather, son and grandson). Starting from the compound,  non-ruler titles that were attested among Bulgarian noble class such as kavkhan (vicekhan), tarkhan, and boritarkhan, scholars derive the title khan or kan for the early Bulgarian leader – if there was a vicekhan (kavkhan) there was probably a "full" khan, too. Compare also the rendition of the name of early Bulgarian ruler Pagan as Καμπαγάνος (Kampaganos), likely resulting from a misinterpretation of "Kan Pagan", in Patriarch Nicephorus's so-called Breviarium[6]  In general, however, the inscriptions as well as other sources  designate the supreme ruler of Danube Bulgaria with titles that exist in  the language in which they are written – archontes, meaning 'commander or magistrate' in Greek, and knyaze, meaning "duke" or "prince" in Slavic. Among the best known Bulgar khans were: Khan Kubrat, founder of Great Bulgaria; Khan Asparukh, founder of Danubian Bulgaria (today's Bulgaria); Khan Tervel, who defeated the Arab invaders in 718 Siege of Constantinople (718), thus stopped the Arab invasion in Southeast Europe; Khan Krum, "the Terrible". "Khan" was the official title of the ruler until 864 AD, when Kniaz Boris (known also as Tsar Boris I) adopted the Eastern Orthodox faith.

 

Eurasia on the eve of the Mongol invasions, c. AD 1200.

 

The title Khan became unprecedently prominent when the Mongol Temüjin created the Mongol empire, the greatest land empire the world has ever seen, which he ruled as Genghis Khan. His title was khagan, or "Khan of Khans", but has often been abbreviated to Khan (rather like the Persian Shahanshah -also meaning "King of Kings"- is usually called Shah,  equally incorrect, in most Western languages) or described as "Great  Khan" (like the Ottoman Padishah being called "Great Sultan"). The great  leader was regarded as a khan in the middle east and Asia. Ming Dynasty  Chinese Emperors also used the term Xan to denote brave warriors and  rulers. The title Khan was used to designate the greatest rulers of the Jurchens, who, later when known as the Manchus, founded the Manchu Qing dynasty.

 Once more, there would be numerous khanates in the steppe in and  around Central Asia, often more of a people than a territorial state, e.g.

• of the Kazakhs (founded 1465; since 1601 divided into three geographical Jüz or Hordes, each under a bey; in 1718 split into three different khanates; eliminated by the Russian Empire by 1847)
• in present Uzbekistan, the main khanate, named after its capital Bukhara, was founded in 1500 and restyled emirate in 1753 (after three Persian governors since 1747); the Ferghana (valley's) khanate broke way from it by 1694 and became known as the Khanate of Kokand after its capital Kokand from its establishment in 1732; the khanate of Khwarezm, dating from c.1500, became the Khanate of Khiva in 1804 but fell soon under Russian protectorate; Karakalpakstan had its own rulers (khans?) since c. 1600.

While most Afghan principalities were styled emirate, there was a khanate of ethnic Uzbeks in Badakhshan since 1697. Khan was also the title of the rulers of various break-away states and principalities later in Persia, e.g. 1747–1808 Khanate of Ardabil (in northwestern Iran east of Sarab and west of the southwest corner of the Caspian Sea), 1747–1813 Khanate of Khoy (northwestern Iran, north of Lake Urmia, between Tabriz and Lake Van), 1747–1829 Khanate of Maku (in extreme northwestern Iran, northwest of Khoy, and 60 miles south of Yerevan, Armenia), 1747–1790s Khanate of Sarab (northwestern Iran east of Tabriz), 1747 – c.1800 Khanate of Tabriz (capital of Iranian Azerbaijan).[citation needed] There were various small khanates in and near Transcaucasia and Ciscaucasia established by the Safavids, or their successive Afsharid and Qajar dynasties outside their territories of Persia proper. For example, in present Armenia and nearby territories to the left and right, there was the khanate of Erivan (sole incumbent 1807–1827 Hosein Quli Khan Qajar). Diverse khanates existed in Dagestan (now part of Russia), Azerbaijan, including Baku (present capital), Ganja, Jawad, Quba (Kuba), Salyan, Shakki (Sheki, ruler style Bashchi since 1743) and Shirvan=Shamakha (1748–1786 temporarily split into Khoja Shamakha and Yeni Shamakha), Talysh (1747–1814); Nakhichevan and (Nagorno) Karabakh. As hinted above, the title Khan was also common in some of the  polities of the various – generally Islamic – peoples in the territories  of the Mongol Golden Horde and its successor states, which, like the Mongols in general, were commonly called Ta(r)tars[c] by Europeans and Russians, and were all eventually subdued by Muscovia which became the Russian Empire. The most important of these states were:

• Khanate of Kazan (the Mongol term khan became active since Genghizide dynasty was settled in Kazan Duchy in 1430s).
• Sibir  Khanate (giving its name to Siberia as the first significant conquest  during Russia's great eastern expansion across the Ural range)
• Astrakhan Khanate
• Crimean Khanate.

   Navaanneren, Minister of the Interior, who along with the 23rd Tushiyetu Khan Dorjsurenkhoroljav (1908-1937) was the last Khan in Mongolia. He was executed during the great purges of 1937.   Further east, in Xinjiang (East Turkestan) flank:

• Khanate of Kashgaria founded in 1514; 17th century divided into several minor khanates without importance, real power going to the so-called Khwaja, Arabic Islamic religious leaders; title changed to Amir Khan in 1873, annexed by China in 1877.

Source: Wikipedia