The wikipedia page on the USRP seems to explain it pretty well: <http://en.wikipedia.org/wiki/Universal_Software_Radio_Peripheral> http://en.wikipedia.org/wiki/

The wikipedia page on the USRP seems to explain it pretty well: <http://en.wikipedia.org/wiki/Universal_Software_Radio_Peripheral> http://en.wikipedia.org/wiki/Universal_Software_Radio_Periph.... It also goes into the issue of daughterboards, although not in-depth. The reason for daughterboards is given as "[...] designed to be flexible, allowing developers to make their own daughterboards for specific needs with regard to connectors, different frequency bands, etc."