All bonds have a CUSIP that identifies the bond in the same way that a license plate identifies a vehicle. CUSIP stands for Committee on Uniform Securities Identification Procedures, which is a part of the American Bankers Association.
Although it's often referred to as a CUSIP number, that is something of a misnomer because a CUSIP typically contains both letters and numbers. The first six characters of the CUSIP identify the issuer, the next two characters identify the issue itself, and the ninth digit is called a check digit, its sole purpose to make computer readers happy. Here's a CUSIP for a General Electric bond: 36966RXR2. Here's one for a Fannie Mae bond: 31396CVP2.