Do herbicides kill bees

Not directly. Weedkiller is a Herbicide, therfore it kills herbage, or green growth.

Pesticides kill pests, or insects which would include bees although they are not seen as pests.

The problem for the bees with a Herbicide is that it kills its pollen plants,therefore it can lean to the death of bees by starvation if a large enough area is sprayed.