What is grain and what are the benefits?

[vonzar]

Hey everyone, I have recently been wondering about grain. I particularly do not like it and think that it hinders an otherwise amazing viewing experience, but I know that the studios intentionally put it in their movies. Is there some reason why they do this. I personally think that there is nothing as beautiful as watching a blu-ray with no grain. I have seen mixed reactions to grain on this site. It seems there are many like me who do not like it, but there are others I have seen who say it makes sense that they put the grain in the movies. Perhaps I am just not getting it, but what is the benefit. I have been buying and watching blu-rays since I got my ps3 back at launch, and never noticed the grain on my 106" projector screen. I didn't know about it until I started watching them on my brother's dlp big screen tv. I at first thought that it was a problem with my ps3, that something had gone wrong with it, but then after posting a thread about it on this site and reading some the comments, and the reading some other stuff on this site, I came to conclude that it was the grain I was seeing. So my questions are, first why do they put grain in movies, and second is grain as noticeable on a large projector screen. I don't get why I didn't see it on my projector screen but it is painfully noticeable on smaller tvs. If someone could enlighten me, it would be much appreciated. Thank you.