I believe the those holes in the right leg of the bench are for pegs, so you can support the end of a plank or sheet of wood whilst the other end is held in the vise. And those holes along the front of the top of the bench are for fitting square pegs in (of different heights) that you can use to hold the front of a smaller piece of wood you are planing (chose a peg height that's lower then the piece you are planing), without having to use the vise.

It's really nice to see an old bench like this still in use. Jealous!