A structure built, quite literally, to be visited
Most flowers carry both male parts, the stamen, made up of a filament and a pollen-bearing anther, and female parts, the pistil, made up of a sticky stigma, a style, and an ovary containing ovules. Pollination occurs when pollen grains from an anther reach a compatible stigma.
Many flowers produce nectar in a gland called a nectary, usually deep at the base of the flower, so that a visiting bee must brush past the anthers and stigma to reach it, picking up and depositing pollen in the process, a trade of sugar for transport.
Bees see a different slice of the light spectrum than humans, they cannot see red well but can see ultraviolet light. Many flowers have ultraviolet 'nectar guide' patterns, invisible to us but conspicuous to a bee, that function like a runway pointing toward the nectary.
Floral scent compounds travel further than colour or shape can be seen, drawing foragers in from a distance, then colour and pattern take over for the final approach and landing.
Once pollen fertilises the ovules inside the ovary, the ovary typically develops into a fruit, and the ovules become seeds, the entire visible fruit and vegetable harvest most people rely on for food starts with this single, brief visit.