Anchored VWAP applies the vwap formula from any bar you pick. Anchoring to a major event shows the average price paid by everyone who has traded since that event, which is often where dip buyers or trapped holders react.
Common anchors are an earnings-report gap, a major swing high or low, or the start of a year.
Example: a stock gaps up on earnings at $120 and rallies to $140. The VWAP anchored to the gap day sits at $131. A pullback to $131 is watched as a place where the post-earnings buyers are, on average, at breakeven.
Related: vwap, volume-profile, pullback, gap