OK, most of the real estate people I know just give me dumb stares when I ask the F/F question and I can't expect you to do any better.
Fannie in now a 5,000 person organization that was an FDR invention to buy mortgages from banks so they could free up capital and lend more
Freddie is now a 5,000 person organization that was a Nixon invention to buy mortgages from thrifts so they could free up capital and lend more.
Read closely.
Then answer 2 questions:
1. Why do we need 2 5,000 governmental entities doing essentially that exact same thing?
2. Why do we need any governmental entity doing what Wall Street can do, that is, create secondary market for mortgages?