Hybrid seeds are totally natural seeds produced by breeders and companies through careful pollination of two specific varieties.
Normally, this highly selective plant breeding is done to bring together two traits in each of the chosen varieties so that the resulting seed has both of the traits. So, for example, one tomato plant may be very drought tolerant and another tomato plant produces vigorously, the two plants might be cross pollinated to produce a drought tolerant tomato plant that produces a lot of tomatoes.
Plants grown from hybrid seeds typically do not produce seeds that can be used to grow the same type of plants and can even produce seeds that will not grow at all.
Though the term “hybrid seeds” is often used in relation to vegetables, any kind of plant that produces seeds can be bred into a hybrid variety, you can even do it in your own garden.