Well. We know that plants have male and female flowers or flowers structures characteristics of males (stamens) and female (pistils) genera in the same flower, so there´re unisexual and hermaphrodite flowers.
Having this clear, then we could mention that plants have male (microgametophyte, or pollen grains) and female (megagametophyte, or ovules in the ovary at the proximal end of the pistil) gametes.
So, for a plant to produce fruit, the first thing which has to occur is pollination, the process by pollen grain reaches the stigma (or distal end of pistil) through different ways (biotic or abiotic pollination).
At this point, male gametes present in the pistil, make their way to ovules after a set of physicochemical reactions inside and between the female flower parts. Then, when these cells reached the female gamete, they fusion together to form an embryo or a zygote (diploid cell) which progressively will grow to form a mature fruit, developing specific structures inside, like the nutritional tissue for the embryo (knows as endosperm) which usually forms that we consume from a fruit.