When you are investigating the rainforests don't forget that rainforests exist on several continents and it's just not about the Amazon rainforest.
As an introduction here is a site with a virtual tour of a rainforest.
Rainforest Alliance's general information page. You could also investigate this organisation as part of your enquiry and find out what they do.
To give you some ideas about why many people believe it is important to save the rainforests follow this link to a mind map created by Paul Foreman on this topic.