A hybrid rice is a variety of rice that has been bred from two very different parents. The seed from the first cross of the two different parents is the hybrid variety. This is unlike inbred rice where the seed of a subsequent generation (usually after many inbreeding crosses) is the variety.
Hybrid rice breeding first requires identifying two optimal parents that when crossed together produce a rice hybrid with desirable attributes including higher yield. Because rice is self-pollinating, crossing the two different parents is difficult and requires one of the parents to have sterile pollen (or male sterility) so it can accept the pollen from another variety. Male sterility can be a genetically controlled trait that can be incorporated into a parent line of rice for breeding purposes.
The male-sterile parent (the one that cannot produce its own pollen) can then be pollinated by the other parent (which is fully fertile), creating the cross that results in a hybrid. The seed born from the male-sterile parent are the seed of the new hybrid rice variety.