Hidden Triple
Column 1 has three cells highlighted in blue at A1, C1 and G1. Between them, these cells contain the candidates 3, 5 and 7, but the candidates 3, 5 and 7 do not appear in any other cell of column 1. Therefore 3, 5 and 7 must provide the solutions for the highlighted cells. The other candidates in these cells are highlighted in magenta, and may be removed.

Hidden triples can also appear in rows and boxes.