Having taken the trouble to customise the system the way you want it, by defining aliases and environmental variables, you need a way to save these setting, for they are lost when you logout. For C shells and their derivatives (e.g. T shell) there are two special script files: .login and .cshrc (the leading dot means they are special files) that help you do this.
If you use the Bash shell as your login shell, then the equivalent of .cshrc is .bashrc. There is no equivalent to .login.