I'm not likely to be taking photos halfway up a crag lol
A hand jam is exactly what it sounds like. You jam a hand or fingers into a crack in the rock as a hold. The climb we were doing follows a crack in the face of the crag and is mostly alright but one section was particularly rough. I suspect someone with bigger hands than me would find it easier going.
Not my photograph and not me but this is the climb we were on.