Finger is a program that tells you the name associated with an E-mail address. It may also tell you whether they are currently logged in at their system or their most recent logon session and possibly other information, depending on the data that is maintained about users on that computer. Finger originated as part of BSD UNIX.
To finger another Internet user, you need to have the finger program on your computer or you can go to a finger gateway on the Web and enter the e-mail address. The server at the other end must be set up to handle finger requests. A ".plan" file can be created for any user that can be fingered. Commonly, colleges, universities, and large corporations set up a finger facility. Your own Internet access provider may also set up information about you and other subscribers that someone else can "finger." (To find out, enter your own e-mail address at a finger gateway.)
Ph and LDAP are somewhat similar facilities.