What exactly happened at Roswell, New Mexico?

My great uncle, if you will, was a scientist. He died a few years back, when I was too young to remember. My grandfather has an attic full of his old military things and I was going through them and found some of my other family member's stuff and to my surprise my uncle's. Some had nothing to do with anything, but a lot of things left me puzzled. I never knew my uncle was a reverse engineer. But he had a lot of things that said he was. Anyway, to the point. I've look it up and can't find crap. In some of these files I have here, it says something about extra terrestrials crash landing in Roswell, New Mexico. On the internet it says that they were taken to Area 51, but I don't really think that's true. On some doents it says things about a laboratory in New Mexico, one place was called Paradise Ranch... Sounds like a dumb code to me. Another has my uncle's signature on the bottom, saying he agrees to terms of something--lot's of it is difficult to decipher mainly because it has marker slashes through pretty much everything. This all got me wondering if any of this is out there. Does anyone else have information on extra terrestrials being here? I'm extremely curious and am open to any information backed up with a believable explanation. And I'd also like to know what exactly happened in Roswell. Why does he have anything to do with it, he was a reverse engineer--that's not military, is it?