In Linux, *nix, finger is a program you can use to find information about computer users. It usually lists the login name, the full name, and possibly other details about the user you are fingering. These details may include the office location and phone number (if known), login time, idle time, time mail was last read, and the user's plan and project files. The information listed varies, and you may not be able to get any information from some sites.
# finger email@example.com