What is Clannnad?

I've seen the ending and a amv to Love Story, but I don't exactly know what it is.
I know it was originaly a dating sim then turned into a visual novel and anime (or the other way around or somthing), but still All I know is that it's a love story about hig schoolers and stuff. I was thinking of watching it but I hate depressing stories.

So my questions is:
What is clannad's story plot?
Does anyone die?
Is it in english?
Is it depressing?

Clanad, yes, it is depressing.

It was made by the same company who created Kanon 2006 and Air, so if you didn't like those then don't watch this. Yes, someone does die. The first 12 episodes are available in English from FUNimation.

As far in as I've watched it, which was the first six episodes, it seems to be more humorous than anything right now.

Ok then I probobly shouldn't watch that, I get depressed really easy

Well, insofar Clannad is much happier than Air or Kanon, I just assume it gets really depressing toward the end.