Gote (後手) is the opposite of sente and implies a move which does not need to be answered and/or which loses initiative.
In this endgame example, the sequence played is gote for Black, since he starts and finishes the sequence.
Gote is not always a mistake, though this page appears in the Mistake path. If a move starts a sequence ending in gote, but the sequence is worth more than twice any available sequence ending in sente, then it might be the best move. This kind of calculation is typical of yose (endgame) play.