This will start you with the default graphical desktop which is probably Gnome. If you would like a little bit more control you can instead type:
This also starts X Windows, but with much less running. To exit X Windows you can press Ctrl-Alt-Backspace. If you have your machine starting in Graphical mode this will just log you out and restart the X server. The GUI interface the X provides can help a lot, especially as you first start learning Linux.