The term "login" is borrowed from the English language. The word itself translates to log (among other things) as "log" and a log with the preposition in – "register" or "login". Therefore, the word "login" can be interpreted as the label in the magazine, it is a name that is used for registration and login.
The username can consist of letters, digits, or combine both. A set of printed characters and must be unique to the system in which you are going to work, you were able to identify and not confused with other users. The second defining criterion is the password. It is needed in order to confirm that you want to access certain information, and not the other person, accidentally scored your login.
Each user comes up with a username themselves. Unlike password, it is recommended to use a short simple name that is easy to remember and type. For example, on any mail service, the username is part of your email address (логин@mail.ru). You not only have to constantly enter your username, to check the correspondence, but also to dictate how to address other people. If the login is difficult, to do so would be problematic.
Registration and logging in with your username give the user the ability to manage your account: edit personal information and to implement a number of actions that are not available to others – unauthorized – users.
On the forums there is such a thing as a "nick" or "nickname", indicating the pseudonym under which a person communicates with other people. Sometimes the username and nickname can be the same, sometimes not. Often, to facilitate registration (and the life of the user) as the login used for the person's e-mail address, a nickname he invents himself. Carefully read the fields that you fill in when registering on the sites to prevent mistakes.