Why do we need password in a server which uses TLS? Suppose a server uses TLS to protect communication between us and the server.

I observe that in the TLS handshake protocol, password is not mentioned anywhere.

Then why do we need to have a password? What is its purpose?
So that the server knows who you are.

After all, TLS protects the communication; however anyone can initiate a TLS connection to the server (unless the server insists that client authentication must be used; they rarely do).

So, if the server needs to make any decision based on who the client is, it needs to find that out itself; TLS usually won't provide client credentials.