A cognitive toolIt is used to help teach the students whatever content area you are currently covering. This could be power point slides, a research paper where you need the internet, interactive learning games, etc.
Communication. In high school and college it can be used for communication with your students or other teachers and staff. In elementary school it can be very useful to contact the parents.
management tools Teachers use computers for grades and report cards. They submit grades to the principle and board all through the computer. It is a very important part of the way that classrooms work.
An evaluation tool It is used for almost all standardized tests these days from reading to writing to math. Even in a kindergarten classroom children take the federally mandated tests on computers.
A motivational tool. It can be used as a reward for students. The reward is 10 minutes of choice time on the computer or with your favorite game. Interaction with this type of technology is what children want these days and so it works as a great motivator.