Limp raising?

[VLV]

I've had this happen to me a few times over the last few sessions. Usually people limp UTG or MP, I bet pot and they would 3bet me.

What does this mean?

I know it depends greatly on the player so lets just divide it into 3 catagories:
15/9/1
20/18/3
35/15/2

And what hands are you calling with against each one of these players? Assume just a standard RR nothing big, but not a min-RR either.