Both.
You might recognise the American version of this as "Knightmare Chess;" this is the French card game, Tempete sur l'echiquier (Tempest on the Chessboard.)
Essentially, the card-play aspect of a Magic or Yugioh modifies the game of chess, creating all sorts of fun. For example, you might be able to double-move a rook, ninja-swap a checked king with a pawn, suicide-bomb one of yer pieces to get rid of all adjacent pieces, or even play mind games like "The next person to say the name of a piece other than King, loses one of his pieces of that rank."