Bee Setting on a brassica flowers.

That's not a bee but a 'hoverfly' (family Syrphidae, order Diptera) which is mimicking venomous insects (for example wasps and bees, order Hymenoptera).
The concept behind this Batesian mimicry is to be protected by appearing like a dangerous insect but at the same time saving the energy which would be necessary to produce venom.

Insects of the order Diptera (flies) have - unlike Hymenoptera - only two wings plus halteres.
Furthermore, if experienced enough, you may recognize the typical eye shape and colour, mouthparts (proboscis) and short antennae of many fly species.

You can find information like this in the post I pinned on top of this community.