Insects, birds, and bats, as well as water, wind, and, in the event of self-pollination within a closed bloom, even the plants themselves, are pollinating agents.
Within a species, pollination is common.
Cross-pollination between species can result in hybrid progeny in nature and in plant breeding.
A pollinator is the agent responsible for the transport of pollen.
Physical pollinators, such as the wind (anemophily), and biotic pollinators, such as insects, birds, bats, and other animals, are examples of pollinators (pollination by insects is called entomophily, by birds ornithophily, by bats chiropterophily).
Insects, notable bees, are the most important biotic pollinators among animals.