Actually a lot of organizations use these two terms interchangable, but from what I have read about this topic in the past. Quality Assurance is a group that creates the processes, procedures, methods of ensuring quality of project or service, while Quality Control is a group that verifies that a product or service meets a certain set of standards.
In smaller organizations this is done by the same group but in larger organizations this is two different groups.
If you do a search on the forum for QA and QC you'll find 10's of threads that have already discussed these in detail and will give you broad definitions from many differ people.
Life should NOT be a trip to the grave with the intention of arriving safely in an cool and well preserved body, but rather to skid in, chocolate in one hand, beer in the other, body wrecked, totally worn out and screaming WOO HOO what a ride!