There are a huge number of commands for Unix out there. Here's a few nice ones to know.
Examples
# Get your current path
pwd
# Returns something like "/home/users/your_username/"
# --
# Check your computers uptime
uptime
# Returns something like "7:48 up 2 days, 8:56, 14 users, load averages: 2.07 2.14 2.22"
# --
# Empty the command line
clear
# This clears the screen for you
# Get help for a certain command
man cd
# This will give you the manual for using the command "cd"
# --
# List the folders in the same folder you're in
ls
# This just gives you a list of the files and folders
# --
# Run a command as administrator
sudo