A pollinator is an animal that moves pollen from the male anther of a flower to the female stigma of a flower. This helps to bring about fertilization of the ovules in the flower by the male gametes from the pollen grains.
Bees
The most recognized pollinators are the various species of bees, which are plainly adapted to pollination.
Bees typically are fuzzy and carry an electrostatic charge. Both features help pollen grains adhere to their bodies.
Most bees gather nectar, a concentrated energy source, and pollen, which is high protein food, to nurture their young, and inadvertently transfer some among the flowers as they are working.
Bees serve a vital role in the ecosystem to help support robust native flora and fauna.
Other Insects
Many insects other than bees accomplish pollination by visiting flowers for nectar or pollen or very commonly, both.
Many do so adventitiously, but the most important pollinators are specialists for at least parts of their lifecycles for at least certain functions.
For example, males of many species of Hymenoptera, including many hunting wasps, rely on freely flowering plants as sources of energy from nectar and also as territories for meeting fertile females that also visit the flowers.
Prominent examples are predatory wasps. The term “pollen wasps“, in particular, is widely applied to the Masarinae—they are remarkable among solitary wasps in that they specialize in gathering pollen for feeding their larvae, carried internally and regurgitated into a mud chamber prior to oviposition.
Insect pollinators include bees, wasps, flies, mosquitoes, moths, beetles, butterflies and lepidopterans.
Vertebrates such as bats and birds as well as other mammals such as possums and rodents and even some lizards can act as pollinators. Among the pollinating birds are hummingbirds, honeyeaters and sunbirds with their long beaks, they are able to pollinate a number of deep throated flowers.
A pollinator is different from a pollenizer, a plant that is a source of pollen for the pollination process.