Watch the Unison Bends online guitar lesson by Chris Buono from 60 Electric Guitar Techniques You MUST Know
Unison bends are made up of two notes on adjacent strings. There's a stationary note fretted on the higher string. On the lower string is the note you bend up to the same pitch to match the stationary note. Together they create this thick siren-like sound that's unmistakable and always super cool.
Looking for inspiration? Classic rock players like Joe Perry and Jimmy Page have littered AOR radio waves with iconic moments in songs like "Walk This Way" and "Stairway to Heaven" with unison bend goodness.