The "hostname$" is what the computer prints, to tell you that it's ready for input.
This can be set using environment variables - the exact environment variable depends on your shell. The most popular shell is "bash".
"man environ" will tell you about environment variables.
"man bash" or "man ksh" will tell you about these shells, including how to set the prompt.
"man chsh" will tell you how to change shells - be careful, you can render your machine inaccessible with this command if you're not careful.
Yes, it takes time to read them and find what you're looking for - this is expected when you use unix or one of its derivatives.
If you're still lost, we recommend one of many good books on getting started with Unix/Linux/BSD and the commandline / shell.
Our eRacks experts can also help do whatever you need to get done on a consulting basis for you if you prefer, or help educate you either remotely or onsite.