What is the difference between authorization and registration through social networks?

Question

In contact with

Hey! Here is an example on Avito. When authorizing and registering through a contact, offline access is required. That is, for anyone, they will add me to the database.
Is it just for convenience? You want to log in, you want to register.

Answer 1

Yes, it's just for convenience.
When authorizing through VK, you do not need to enter a password and mail. No need to remember/write down the password. This is the whole point, to access the site, you already have an existing VK account.

Answer 2

The user spends less time, as a result it is more conversion

Answer 3

I'm stunned! I meant authorization from registration :)