Check the fraud score, view supporting information including true country, operator, proxy status, and Tor status. (thanks to Fayne for bringing this down)
Search your IP and check!
Q - What they can do with it?
A - You can use these sites to check if your IP has got a good reputation or not.
Q - What peoples can do with my IP or site do with my IP?
A - They can not do much, every site you visit sees your IP. This site can show you if your ip has a bad reputation though.
Good luck & enjoy it!