The term Anchor Step is used to denote a dance step in which you should not come towards your partner at the end of a pattern.
An Anchor is NOT a foot position and not a Rhythm. It is a partner connection in West Coast Swing, achieved when both partners place their CPB (Center Point of Balance) behind the heel of the forward foot. An Anchor is danced on the last two beats (last Unit) of each basic, fundamental Step Pattern in West Coast Swing. A feeling of body leverage balances the resistance of both partners. Each partner is responsible for establishing their own individual anchor.
Different types of anchor will leave the partners in one of three positions: 1) the dancers are not individually centered (with an away resistance), resulting in a heavy active connection (sometime referred to as leverage; 2) partners will be individually centered, resulting in a passive connection; 3) the follower's center point of balance will be slightly forward of being individually centered - resulting in a passive connection.
The term "ANCHOR" was coined by the Golden State Dance Teachers Association in the early 1960s to clarify the difference between the "resistance" desired at the end of a West Coast Swing Pattern, and the lack of resistance caused by one version of the second set of triples taught circa 1961.
The anchor step is the terminating step pattern of nearly all main West Coast Swing dance moves. Together with the slot, it is the most distinguishing element of West Coast Swing as compared to other swing dances.
In its standard form, the anchor step consists of three steps with the syncopated rhythm pattern "1-and-2" (counted, e.g., as "5-and-6" in 6-beat dance moves) and the general directions of steps "back, replace, back (and slightly sideways)" danced almost in place. The leader dances R-L-R feet, the follower dances L-R-L.
At the end of the anchor step the partners settle their weights on the "back" foot, the handhold is typically L-to-R, with leverage connection maintained throughout the step, and there is no urge to go in any direction in the end: the parthers are "anchored" in this terminal position at their respective ends of the slot (hence the name of the step), ready to commence the next move according to the leader's lead.
Pulled from: http://en.wikipedia.org/wiki/Anchor_Step