Dont Pull The Plug How To Shut Down Or Restart Your Raspberry Pi Properly

sudo halt

This is shorthand for the following:

sudo shutdown -h now

An explanation:

sudo - run the command as superuser
shutdown - shut down the pi
-h - halt after shutting down (do not reboot)
now - do this now (required time command)

sudo reboot

This is shorthand for the following:

sudo shutdown -r now

An explanation:

sudo - run the command as superuser
shutdown - shut down the pi
-r - reboot the pi after shutting down
now - do this now (required time command)

You can also safely shut down the Pi by adding a Pi power button!

How to Add a Power Button to Your Raspberry Pi
Because you should always safely shut down your Pi.