Simplified, NGOs are trying (or supposed to be trying) to do things they believe are good. Much of the work is development-based, going into specific genres like rescuing street dogs or providing vaccinations to a Ugandan village. On the other hand, NGOs can be much less hands-on, and some are devoted to lobbying politicians or raising money to delegate to causes they find worthy. This site focuses particularly on NGOs that provide education, medical aid, development services, environmental protection, and human rights advocacy. Whatever the case, the intention of a good NGO is to foster goodness in the world.
Unfortunately, this hasn't always been the end result. As with anything, when large amounts of money are being dealt out, corruption and malice manage to work into the mix. For example, Philip Morris (the cigarette conglomerate) is one of the largest business donors in the world, yet many believe the intention is to create a clean reputation for a company distributing poisonous products. Likewise, there has been huge concern lately with orphanages that are touted as great volunteering experience, helping children who really need it, but turn out to be more like slumlord business for the people running them. It's a sad consequence but one to be aware of: Not every company supplying large chunks of money is well-meaning and not every organization is doing what it says it is.
Like most things, though, 90% of people are out there to do good, and usually it's easy enough to spot the ones who are. For the purposes of this site, we try to promote NGOs we've either had first-hand experiences with or done a great deal of research about. We've done my best to introduce readers to places that will provide a fulfilling experience for them, as well as could honestly use a hand or two getting the job done.