Well there's no explanation necessary here, is there?
Facebook is actually quite a bit older than you'd imagine, becoming an incorporated company in 2004, and being founded by Mark Zuckerberg. Originally Facebook was only open to students of Harvard university, and mirroring its popularity today, half the undergraduate population were registered within the first month. So how has Facebook gone from such a small, localised scale to operating on the vast, global scale it does today?
Becoming gradually more and more open, first to other Ivy League institutions and then to employees of Apple inc. and Microsoft, shares in Facebook were bought by Microsoft in 2007. This was arguably the point at which its growth began to accelerate rapidly, and also when it was opened to anybody aged over 13. From this point onwards, it became a phenomenon among teenagers, and was the point Facebook went from being a form of recreation to a global commercial enterprise.
Facebook has changed the lives of many forever, particularly university students, although do the positives outweigh the negatives? It's fun, and useful for seeing what your friends are up to and where they are. But it's also a time waster and the most popular form of procrastination. Most do not think about the implications of what they post on Facebook, indeed people losing their jobs through regretful posts have become all too common. There is also the huge issue of young people using Facebook, who are often lulled into a false sense of security by the privacy settings, which still don't make Facebook as private as it may seem.
In short, Facebook has definitely had a positive effect on our social lives, but on other aspects? If you ask me, it's caused nothing but trouble.