Primary is where your fermentation takes place. A secondary is often (wrongly) called a fermenter, but no fermentation should take place. Some people use it as a clearing tank. You move the beer off the sediment in your primary. Secondarys can be used for long term aging or I use them to make extra additions to my beer - coffee, chocolate, chicory, etc ...

Here's my line up.

Primary:
Coffee Malt Stout
Coffee/Chicory Stout

Secondary:
Robust Porter

Bottled:
Nut Brown Ale
Gamera's Double Chocolate Stout
Hall & Oatmeal Stout
Sweet Stout
Christmas Ale