What Does It Mean When Someone Acts Nervous Around You?

If they're the opposite sex , it means they like you!

If they just get nervous around you, then they are attracted to you. I am a very shy person and I do this when I like someone. Whenever they come around I get even more quiet and nervous, and I even physically distance myself from them. Shy people usually do this because they are afraid that they will look stupid in front of the person they like. And they don't have to be the opposite sex to be attracted to you.
 
Sorry, I meant to answer the question in the first place, instead I accidentally commented on someone else's answer ;)
 

They like you.