When the worker bee visits a flower, she uses her proboscis to extract the nectar from the part of the flower where it is stored. The nectar is sucked into a honey sac, which is basically a second stomach.
While collecting nectar, powdery pollen brushes off the stamen, the male reproductive part of the flower, onto the bees hair. Using brushes on their legs the bees transfer it to pollen baskets on their hind legs. As bees move from flower to flower they pollinate the flowers.