apple trees

You only have to look back in history to answer this. Bramley seedling and Cox's Orange Pippin both emerged from a hopefully planted seed.
That's not to say that yours will be as successful, but persevere and be patient. There's a 99% chance it will produce something.

99% chance it will produce a crab apple, sadly.
They take about 5 years to get to a size where they can produce fruit. Since they are on their own roots, then the chances are it will eventually grow into a very large tree.

The fruits are either going to be really decent and pleasant tasting or really unpleasant and not worth it. Didn't think it would necessarily be a crab apple thou?

A Crab apple is any non culinary one. So you have Eaters, Cookers, Cider and Crab apples. Malus domesticus (covers all forms of Apple) is reckoned to be the plant most capable of variation from seed. Every pip in one apple can produce something different.

SO it can be anything, the proff is in the eating! Or size of the fruit