Why are they there? Most of the music of that time was written for either the harpsichord or clavichord and they didn't have the sustaining power of the modern piano. Ornaments were a way of doing that and also embellishing the musical lines. There are different ways of interpreting them so you need a guide for execution. Some were written in by the composer and others were put in by people who think they know more than the composer. They are generally played so the edition you have should have a page that shows how the various ones are executed. If not, then a dictionary/encyclopedia of music should have them in it. Then there are books published just on that subject. If you are with an instructor then they should apprise you of the mode of execution. Are they all the same in all editions? No!! Find as reliable an edition as you can and then follow it. Don't worry when somebody questions it--they're probably no more informed than you but are just using a different edition. Some instructors go through and mark additional ornaments or change them or delete them. It means they think they are authoritative enough to do that. If you care to do so, you can buy an URTEXT edition (printed as the composer wrote it) and forget anything else.
Good luck! You just opened up a can of worms!
Do what your instructor advises tho.