OK, well your best bet is to search for the terms you're interested in, not just post a request for info then sit back. Also check your spelling; if you get no hits then that could be why. Desision and suport are not correct; try decision and support instead. It's unfortunate that the main language of the internet is English, but it has to be something, and non-English speakers just have to get used to it.
Contrary to your teacher's implications, forums are *not* full of people just sitting around waiting to answer your questions in painstaking detail. We will help, but not do your work for you, and we *can* tell the difference. This site is called go4 *expert*, remember, so that means we're expert at a number of things.
The best place to search is Google. Did you try? I've just tried it and there were several hits that looked appropriate. Google also has a good guess at fixing spelling mistakes and "desision suport systems" gives a list of hits titled "Showing results for decision support systems".
The Wikipedia article will most likely tell you everything you need to know, and more, about DSS, and most Wiki articles link to lots of other relevant places.
This is an excellent reference on how to ask questions intelligently:
Read this *thoroughly*, and act on it, and you will get good answers to your questions.