IP address score is a rating given based on the activity of the IP address. If the IP address did not participate in any spam (illegal) activity then the best rating is given 0. If the IP address participated in any spam activity then a rating is given that is greater than zero, and its size depends on the intensity of spam activity.
IP To Host. IP To Host will give you hostname of an IP Address. For example this IP tool show that an IP address 98.138.253.109 have hostname ir1.fp.vip.ne1.yahoo.com Domain To IP. Domain To IP will give you an IP Address of Domain or Hostname. For example domain bing.com have an IP address 131.253.13.32 and hostname bingiton.com