A psychic vampire essentially feeds off psychic energy rather than blood.  It's also a little more passive, as psychic energy can be siphoned slowly without making contact, though it can be absorbed more quickly if the vampire makes skin contact with their source.  Like sanguine vampires, the psychic vampire has to feed from a living source (i.e. not other vampires of any kind).  I could come up with more specifics if you need them, but these are the basics.