I am so confused!

Ok, could anyone explain me what's the difference between this and Ju-on(2000)?

and what's the difference between Ju-on 2(2000) and Ju-on: The Grudge 2(2003)?

Are Ju-on: The Grudge(2003) and Ju-on 2(2000) the only Ju-on movies that we can find on DVD in the US? These are the only one I could find(didnt watch Ju-on 2 yet...), but seeing that Ju-on 2(2000) is the sequel to Ju-on(2000) then what relation does it have with Ju On: The Grudge(2003)? Odd that they released the sequel to Ju-On(2000) on DVD in the US, but not the original one... That's freaking dumb...

I am so confused and I'm pretty sure my post is confusing too lol, so read carefully! Help please!

PS: I'm not talking about the remakes, but about the Japanese movies...