There isn't really a long way to say this, but yes it does.basically you turn completely into the foes type.
Example battle situation.staryu vs deskill.
Staryu uses reflect type
Staryu is now the ghost type so if it canlearn shadow ball and has it,it can use shadow ball and get stab and supereffective damage.
Beware! If using this on a ghost or dragon type,using reflect type ca backfire! Becuse ghost and dragon types are weak to themselves,they can be hit by the foe after they use reflect type for supereffective damage!