"RAW files" are generally the native format that is saved by DSLR's (and some compact) camera's.
you could say it contains the used settings to shoot the picture and a dump from the sensor. "Raw files" allow you to change the whitebalance , exposure (within certain limits) and a lot of other parameters after wards in photoshop or a other capable editor.

If interested see http://www.luminous-landscape.com/tu...aw-files.shtml

PSD is the native format of photoshop and has no relation to camera's as such.