well i saw that there are 3 seasons, i would like to know the other in which i have to see them
The answer to this question for any multi-series franchise is almost always "Watch them in the order they were created," which you can look up on AniDB and the like. Except for ones with a ton of alternate timelines and continuities like Gundam, Macross, the Leijiverse, Bubblegum Crisis, etc. But the
Relations Graph for ARIA is very straightforward.
Like others have said, ARIA is about escaping to a beautiful world free of unpleasantness or major conflicts. It's all about relaxing, forgetting the troubles of the real world, and crying happy-sad tears. Most of the episodes are standalone stories that fall into one of two broad categories: Character interaction & development; and Supernatural Mystery (concerning hidden places, spirits, cats, strange phenomena, glimpses into the past, and other wonders of Neo-Venezia). There is an over-arching plot concerning Akari, Aika, and Alicia's progress as Undines, but you have to watch from the beginning of Animation through all of Natural to the end of Origination to see it. I remember Origination was extremely well-reviewed on AniDB at first -- for awhile, there were 3 perfect 10.0 reviews, and I couldn't really contest those scores. I think this led to people with no previous Aria experience checking out Origination because of the wow-Amazing reviews, and being left thinking "what the hell is this stuff?"
As personal testimony, Aria the Natural played a big part in helping me deal with fast-food work bullshit back in 2006-07. Well, that and shameless wish-fulfillment like Dears
Also Pani Poni Dash. And Captain Morgan's Private Stock between split shifts.
