See the surface type you have: (click here to see them all.)
Most people have no idea about the history and characteristics of their flooring. You can click this link to see how to easily test with water drops and understand which sealer is most appropriate for your goals.
Some questions you may not be thinking to ask right now that could become important:
. Was it sealed in the past? Does that matter?
. Will a new sealer be compatible with whatever was used before?
. What sealer will give the visual results you want?
. Will you also be able to have a sealer solve problems? ( Answer: yes. Just know which to pick.)