Pollination is "the transfer of pollen from the stamens to the pistil". Pollen is transferred primarily by wind (for instance in grasses and conifers) and by insects (mainly bees, butterflies and moths, in most flowering plants), but also by water and vertebrates such as mice, bats and birds (e.g. the hummingbird).
Pollination can occur both within the same flower and between different flowers, either or not on the same plant. In which of these cases pollination leads to fertilization depends on the specific properties of the plant species.