What does the following mean: "MORTGAGE-BACKED SECURITIES PROGRAM SUPPLEMENT TO PROSPECTUS DATED JULY 01, 2004"?

What will be an ideal response?

When issuing MBS, the GSEs provide a prospectus for the offering. What is issued first is what is termed a "prospectus." However, the prospectus contains general information about the securities issued by each GSE and the risks associated with investing in MBS securities in general. The prospectus is amended periodically. It does not provide specific information about the loan pool for a security. That information is provided in a supplement to the prospectus, called the prospectus supplement. This information is provided to assist the investor in assessing the value of the security or, more specifically, assessing the prepayments that might be expected from the loan pool. Thus, "MORTGAGE-BACKED SECURITIES PROGRAM SUPPLEMENT TO PROSPECTUS DATED JULY 01, 2004" refers to the information needed to assist the investor in understanding the offering.