A reverse sente play is a play which forestalls a sente play of your opponent and ends in gote. Reverse sente moves are rarely played, as the player with sente will normally be able to play the sente before the reverse sente is profitable.
The hane-connect, - , is sente, threatening to save the stone.
The hane-connect, - , is gote. It forestalls the White sente and gains 3 points. The endgame value of this move is said to be "3 points in reverse sente", which works out to just "3" in miai counting.
Non-mathematical explanation of when to play a reverse sente: if there are 3 remaining yose plays and 2 are gote with the same value, then play the reverse sente first. (See further reading).
It is traditional to divide moves into four categories: compare reverse sente with sente, double sente and (double) gote. However, for many years, go professionals have recognized that double sente is problematical. Also, Bill Spight has added a new category for ambiguous plays, which are not simply sente or gote.
When to play a reverse sente - The assumptions and the mathematics required for working out the endgame value of reverse sente
Sente gains Nothing - One-sided sente plays "belong" to the player who can play the sequence in sente.