Hi zinc30, Welcome to Physics Forums!
We have a saying here: “Google is your friend”. That means using it to search for definitions and explanations of natural processes. You’ve asked a very basic question, and it is an important one. But you have not shown that you’ve tried to learn the answer on your own. We do not spoon feed others here, no matter what their age is.
Wikipedia is a good place to start with many subjects in science. It’s not 100% reliable, but usually gives a good introduction and explanation. When you search Google using the term “photon” you find the Wiki entry on the first page. The first part of the first sentence is “A photon is an elementary particle, the quantum of light and all other forms of electromagnetic radiation, and the force carrier for the electromagnetic force,...” Notice please, the “Contents” list near the top of the page. Seventeen sections are presented, including complete references for further detailed study. Here’s the link:
http://en.wikipedia.org/wiki/Photon
Here’s my recommendation: Go to that Wikipedia page and read it completely. Then, when you have some specific detailed questions or doubts, come right back here and post them. Members here on Physics Forums are always willing to assist a true searcher trying to learn more science.
Cheers,
Bobbywhy
EDIT: davenn beat me to it while I was writing this. He linked to the same page!