The transfer of pollen (male reproductive cells) from one flower's stamens to another flower's pistil, enabling fertilization and fruit/seed development.
Pollination happens when pollen reaches the pistil of a flower. Wind carries pollen in some plants; insects (bees, butterflies) carry it in others. Successful pollination leads to fertilization and fruit/seed production. Without adequate pollination, fruit doesn't set and yields drop.
Understanding pollination explains why some plants need pollinators (bees), why some need cross-pollination, and why some are self-fertile. This determines planting choices.