I've chosen to study informatics and that's why computer is necessary for me. First of all I'll need it to program. I learn programming languages such as C++, Java and others. Also I use computer for solving various mathematical tasks. It is quite useful in solving very difficult propositions. For these purposes are used special mathematic programs such as Mathematica, Mathcad, MatLAB. I must say I need computer to make assignments of maths, english, and other subjects. Furthermore I work with application programs. For example, I use word processor to write papers and essays, I make presentations using special programs. Computer also is needed for me to find the information I need. For this purposes I use the Internet. I have some dictionaries, which I use for translating words and studying English.
But I use computer not only in my study but also for entertainment. Browsing the internet, I find much information about things that interest me. Chatting on IRC is very practical. I chat with my friends without spending much money, because I don't have to call them. Moreover, I am trying to work with media editing programs for photos and videos, but I do it very rarely.
So as you can see computer has become quite essential part of my life. I can use it in many ways.