What is the use of Tuser in PasswordHasher class

[ashu10832]

In the PasswordHasher class, the hashing function takes a Generic type Tuser, but we are not using the variably anywhere. Can someone please explain why are we using it. Link to the said class is mentioned below.

https://github.com/dotnet/AspNetCore/blob/master/src/Identity/Extensions.Core/src/PasswordHasher.cs

[ashu10832]

Also, if a random salt is generated everytime, how does it verify the password without taking the salt as a parameter?