Seafood is food mainly consisting of marine animals like fish, crab lobster and so on.
Seafood dishes are generally delicate in their consistence, since most marine animals meat is delicate, except Tuna and the likes, which can be like a tender steak.
Seafood is considered a delicacy in most places because the delicate meat quickly begins to rot, thus seafood is best when it is as fresh as possible. And since it is difficult to get really fresh fish anywhere else but near the sea, the good seafood restaurants are always near the sea.