Suppose I have just refinanced my mortgage (and realized significant cash flow improvement, thank you very much!), and in the mail this week I received a letter informing me my mortgage has been sold to Freddie Mac. Further suppose I do not have a lot of financial knowledge.

Explain to me in straightforward language what the letter means, the process it is informing me about. Explain why this is a good thing for the mortgage market despite the financial crisis. Also, include a brief explanation of Freddie Mac and its current circumstances.