Question

What is self pollination and cross pollination?

Answer 1

Transfer of pollen grain from the pollen sac of a flower to the stigma of the same flower or stigma of a flower borne on the same plant is called self pollination.
Transfer of pollen grain of a flower to the stigma of a flower of a different plant of the same species is called cross pollination.

Answer 2

Cross pollination is the transfer of pollen grains from the anther of a flower to the stigma of a flower of a different plant of the same species.
Self pollination is the transfer of pollen grains from the anther to the stigma of the same flower.