As mentioned above, the forefinger can be used for pointing. However, this gesture is considered rude in some countries (Brunei, for instance), and other gestures are used instead.

A lone index finger often is used to represent the number 1, or when held up or moved side to side (finger-wagging), it can be an admonitory gesture. With the hand held palm out, it represents the letter d in the American Sign Language alphabet. In sports, it can also represent victory, as some championship-winning teams raise their index finger while posing for a championship team photo.

During the Bosnian war, Serbo-Bosnian troops raised three fingers in a sign of victory, Bosnian Croats raised the two-finger V-sign and Muslims raised one (after the strict monotheism of Islam).

The two index fingers are generally used for hunt and peck typing.   Which is not to be confused with the one handed (two fingered) typing I've been doing for the last two weeeks following my elbow sugery.