Many countries have different categories of visa. The simplest is the transit visa, which gives you a very short stay while you are waiting to travel somewhere else. Next is the tourist visa, which allows you a longer stay for the purpose of tourism (just visiting). Then there are the more 'serious' visas like business visas, study visas and longer-term family visit visas.
Obviously, the checks done for a tourist visa (they basically just want to be sure that you will leave by the end of your permission to stay) are much less than those done for a business visa - the intention of the tourist visa is that you will visit, then leave.
However, if you intend to study you should apply for a study visa. Check this page out for details.
Doing anything outside of what is permitted by your visa is usually a very serious offence, so it is important to get the right visa for your stay - penalties can include a fine, deportation and imprisonment while the case is being dealt with.