What is the meaning of authentication through social networks?

Question

Drupal

Folks, if authentication takes place through a social network, do I understand correctly that:
1. the login, password and identifier are stored in the site database (if without extra fields)?
2. Can the password be retrieved from the database?
3. What are the advantages of such a login (through social networks) for the social networks themselves, what is the benefit for them (collection of behavioral data, what else?)?

Answer 1

1) no
2) no
3) just convenience

Answer 2

1. Watching how to write.
2. If the password is from a social network, then no. In most cases, a user is also created in the system to which the social network is attached. This password is possible, again it depends on how the authorization is written. From the social network, you can save, get and use a token with which you can do a lot of things in the social network.
3. First of all, this is convenience. Secondly, with a strong need and desire, you can do everything that the user allowed for the token: post on walls, groups, upload photos, etc.

Answer 3

Hello, it is not clear from what fright you came to the first conclusion, from here all the following is nonsense.

Answer 4

so that all doubts and questions disappear, just briefly drop, for example, the device ulogin.ru