here it is told about the HEART framework

HERT- Happines Engagement Adoption Retention

                                                                                     Engagement 

  Engagement is a logical continuation of activation (which we talked about in the previous paragraph): the answer to the question, do users continue to benefit from the product?
  Relatively speaking, a Slack user has invited ten colleagues, which tells us that they are all interested in the product? For example, the following engagement metrics:amount of time spent in chat per user;number of active channels;

the number of direct messages per user, and so on.
Engagement metrics are also great for measuring project success:in the case of customer-facing features, engagement should remain at the same level (provided other metrics improve) or grow;in the case of infrastructural changes, engagement should remain at the same level.

                                                                                          Happiness

  As much as all companies would like to improve the user's happiness, they also do not know how to count it: emotions are not as easily measured as DAU, for example. The question is whether this is needed at the product level.
  I use Spotify every day. Am I a happy user? In my opinion, this is as strange a question as - you use a hammer, are you a happy hammer user? Emotions are about a brand, about a story (which, by the way, is marketing); product - about solving a problem, about value. Users may have some feelings for Yandex or Google, but not for the search engine as such - here they have a purely rational approach.
  Again, if we are developing a function (these are project metrics, we mentioned them above), then we have to think about product metrics - and then the same NPS, for example, is completely useless: it is almost impossible to measure the impact of a single function in this way.
  It's another matter if we ask: does the user get any benefit from our product? The concept of value (or happiness) is also great for prioritizing new features.
 How to determine value? Go backwards: ask yourself - if we imagine the ideal user who gets the most out of the product, what does he do?

                                                                                           Adoption

 But here we need to go back to marketing and product metrics. Adoption is just a great example of a metric that sits somewhere at the junction.Could an improvement in product quality or a cool new feature increase the number of new users? Maybe. Can an ad campaign or blog post increase registrations? Maybe.
 In my practice, the second happened more often than the first; it is quite possible that due to the specifics of the products with which I worked. Another important factor, why I still attribute this metric to marketing more, is user habit.
 A small number of people regularly check how your product has been updated, especially if they are already using a competitor and have created some kind of process around it (for example, when I go to work, listen to podcasts on Spotify) or, even worse for you, added your personal information (for example, when I take photos with my phone, I upload them to iCloud).
The longer the user uses the product, the higher the switching cost is likely to be. Thus, to get a user to go to you, you either need a competitor to have a visible flaw that you do not have, or you must have a killer function that the competitor does not have. In both cases, this suggests two options.

The user seems to like everything, because he does not know how it could be better - marketing informs him about the alternatives.
The user is dissatisfied with the current solution and uses it because he does not see or did not find the best options - he needs to tell him about them using marketing tools.
Of course, there is also the word of mouth factor, when users are delighted with a product and share recommendations with friends. But in my opinion, from a product perspective, this is better reflected by three other metrics:activation (whether the user has realized the value of the product);engagement (whether he continues to benefit);retention.

                                                                                         Retention

    There is little to add here: retention for most services is one of the most important product metrics. In my practice, retention and engagement determined the success of a product or feature and most closely matched the value the user receives.
   The outflow does not work at the function level, but it will probably be the loudest bell that something is wrong with the product. It is clear that there will be a part of users that will leak out for natural reasons; we are most interested in the users who have passed the activation and decided to leave.

 If you want your product design to be informed by data, think about metrics that reflect the quality of the user experience and link them to your core goals.