The Quad Flat Package (Or QFP as it is abbreviated) is a form factor for ICs, especially surface mount ICs. It is the later kindred to the Dual In-line Package or DIP and is used for easily replaceable chips.
The QFP is a square ceramic package with leads fixed on all four edges (instead of only two as on a DIP), and many have rounded leads for use in sockets as opposed to the 'spider' pins of the DIP; this makes them much sturdier and can better handle repeated removal and insertion without damaging the leads.