Here are some links to help you go further with logic gates.
Go to the wikipedia page on logic gates and examine the diagram for the 7400 chip. Now you will understand why solid state memory on flash drives, gaming consoles, etc is called NAND memory. http://en.wikipedia.org/wiki/Logic_gate#Universal_logic_gates
Go to this site and watch any video of your choice – http://www.yourepeat.com/g/logicgates
If you can’t pick, then go with the one which shows how computers add numbers. http://www.yourepeat.com/watch/?v=VBDoT8o4q00