Velveeta is a processed cheese that melts well.  Growing up my mom would make mac n cheese with Velveeta, butter, and of course pasta.  I still have mac and cheese with Velveeta when I get a craving for it.

I also use Velveeta to make Velveeta Cheesy Chicken and sometimes for Better StoveTop Mac and Cheese from a Box.

Want to know more about Velveeta?  Check out Velveeta on Wikipedia.