modeller, the key above the caps lock is called a 'Tab key',
the key below the Caps lock is called a Shift key (this is used when you want to convert a lowercase to an uppercase)
When my mouse stops working i usually use the 'tab' key to help me work around this site etc. If you press the tab key once, you will see the curser will disappear and you will notice the 'submit' button looks like its pushed down, just like as you move your mouse over the submit button. If you press enter then the button will activate and acts just like as you click onto the button. So really the tab key is used when you dont have a mouse.
Say for instant you press tab now and it jumps into the submit button but you want to go back then you hold on to the Shift key and press the tab key, you will see the curser back in the text field.
again for the Alt button, if your mouse dosnt work then you use this button to get to your menu's, ie ifyou look at the top of your webpage you see file > edit > view etc, if you want to get into file then you hold on to the Alt button and press letter F (you will see the letter F is underlined) without using your mouse, you use the arrow button to work your way round it. it is pretty usefull when you dont have a mouse working.
hope this helps :-S or make any sense lol its so hard to explain :p