What kind of interface do i need? If i need one?

Im new to the whole music production industry. I plan on buying a Axiom 25 MIDI KeyBoard and using Logic for software. Okay now im only going to be producing music only using samples and digital sounds/beats found in the software....no guitar , no singing .... My question is what kind of interface do i need to get, and do i really need to have interface? will it require me to buy any extra cables? What exactly does the interface do?