Is the use of username/password in a mobile app needed? [duplicate]

1. What is the purpose of a username and password?
2. Is my username the same as my password?
3. How do I use the same username in Salesforce?

What is the purpose of a username and password?

The Importance Of Usernames And Passwords

It's used to build a unique digital profile about you specifically. For example, your username for an online retailer would be connected to information like your shipping address, credit card number and shopping history.

Is my username the same as my password?

The username is an identifier: it tells the computer who you are. In contrast, a password is an authenticator: you use it to prove to the operating system that you are who you claim to be. A single person can have more than one Unix account on the same computer. In this case, each account would have its own username.

How do I use the same username in Salesforce?

A username can only be used once. When receiving 'Duplicate Username found' or 'Username already exists' error message, either pick a new username or have the User with the existing username change theirs.