Well, getting a perfect definition of the blockchain is a very tedious task. Blockchain has evolved so much in recent days and has shifted so much from the very basic concept. But a newbie just need a basic description to get started.

Now take for instance you are moving to new location and you'll need to sort your belongings into separate boxes. For organizational purposes, the boxes are filled and arranged 'as they come'. Now, to make sure you don't lose any of your important belongings, these boxes are tied to each other in an orderly form. Now, your boxes are the blocks, the material used to tie them to each other is the the chain. This is a very basic representation of the blockchain.

According to your arrangement of these boxed and how you tied them to each other, you'll need to repeat the whole arrangement before you could change the position of any the boxes, and of course, each box is sealed so it is almost impossible to change anything in your arrangement. When you get a new box filled, it is attached to your arrangement. This is how the blockchain works.

In the blockchain, each block is container of data, these data could be transactions, state changes, mining details e.t.c (just as you can pack anything into your box in the example above). Each block is connected to the subsequent block via hexadecimal identification stamps, this is the chain.