Just as "tramp stamp" is to lower back tattoo, "Welcome Matt" is to lower abs. Right above a chicks pussy. It gives you a little taste of what she is like.

A pick me is a woman that is willing to do anything for male approval. She will embarrass or throw other women under the bus to achieve this goal. The unfortunate thing about a pick me is usually the men they are trying to seek approval from are of poor quality and treat women badly, leaving little real benefit for the pick me.