Medical Certification
Medical Certificates are broken down into First, Second and Third Class. To exercise the privaleges of a student or private pilot, you need a valid 3rd class medical certificate or greater. The requirements are not horribly strict, but you do need to be in good health.
You will apply for a medical certificate with an Aviation Medical Examiner (AME). Prior to your visit, you will want to obtain medical documentation for any conditions you have, in order to speed the process along.
Basic requirements for each class of medical can be found here
If you have any questions about a condition you have, the best place to start is AOPA's Turbo Medical form. This requires a membership with AOPA, but it is worth it at $39/year for all the help they offer.
If you do have some sort of medical condition, it is very important that you show up to the AME fully prepared. It is much harder to get a medical after it has been denied, than it is to get one having never applied before.