F1 seeds are the first generation cross between 2 different parents.
They cost more and you can't save the seed to get the same again, they babies won't be the same.
I'm sure someone will give you the upside of these. I don't use them
F1 hybrid seeds give you a very uniform batch of plants, often vigorous and with high yields (for veg). They are produced by deliberately crossing 2 stable parent plants with characteristics you're looking for, and making sure no pollen creeps in from any other plant - so the offspring of the cross, the F1 hybrids, will be well-nigh identical to each other.
F1 seeds tend to be much more expensive than open-pollinated varieties, and you may get very few seeds in a packet. They are often used by commercial growers who want, say, a field of brussels sprouts which are all ready for harvest at the same time - that might well be less useful for the gardener, who would like their sprouts ready in succession, over a number of weeks. F1 flower seeds will produce plants which are the same height and vigour, useful if you're doing a bedding scheme.
A lot of popular flower and veg seeds are not F1 hybrids but are open pollinated, or F2 hybrids (more variable than F1, cheaper, formed by crossing two F1 varieties) and are perfectly acceptable for the home gardener.
If you do some research online about recommended varieties you'll get a lot more information!
I buy F1 only in order to get a particular variety that I can't get otherwise, such as Sungold tomatoes; or if I only want a very few plants anyway (say, courgettes) and don't mind only a few seeds.