I'm doing a presentation on operating syster. and I need to know what is it and where is it used today. Does anybody know where can I find information on it?

Which operating system? There are plenty. Unix, Windows, DOS....

what kind of information do you want? there's tons of stuff you could talk about, but a lot of it would be getting pretty technical.

you could talk about what an OS is, the difference between different OSs, what those different operating systems are (DOS, Windows, Mac OS, Unix, Linux, FreeBSD, the list goes on...), OS history, the people who have developed some of the more popular operating systems, etc.