whoami tells you your current username.
$ whoami abicool
groups states the groups the current user is a member of
$ groups wheel slocate www
id gives you the same information as the whoami and groups commands, but also includes the user id (uid) and group id (gid) integers associated with the login.
$ id uid=3426(alice) gid=10(wheel) groups=10(wheel),21(slocate),401(www)
tty tells you the terminal device that is assigned to your interactive login. The tty represents your console device, network connection ("ssh", ...), or terminal emulator process ("xterm", "konsole", ...).
$ tty /dev/pts/14