Please HELP! And PLEASE no plagiarism.

1. What does “SPF” mean and will it protect me from the sun’s rays?

2. I heard that the most common type of skin cancer you get is called basal cell carcinoma. Why is everyone so concerned about this type of cancer and is it treatable?

3. I read somewhere that medication can be photosensitive. Why is it important to know if a medication is photosensitive? How would I know if I am taking a medication that is "photosensitive"?