Single Player to Online Player Question

Hello everyone. I just recently bought Diablo and I have a question about the point of a Single Player game. Is it just to adventure into the depths of the Diablo world? Or is there a place you can connect with other players to do things?
Also:
Online, once you get into a world, what do you do? It's just confusing... Is there a special point to playing it online?
Thanks for helping!|||The point of playing Single Player is for people that don't have an internet connection (imagine that) or just want to play solo in a safe environment.
Playing online allows you to party up with other players (and different character types) to quest together as a group. There's also PvP (Player vs. Player) where players get together to duel each other.
When playing online, watch out for hackers (cheaters).
Whatever you decide, good luck and have fun.
Justin|||I'll elaborate on Justin's post a bit and hopefully I won't confuse you.
I'm assuming you are playing Diablo 2. Diablo 1 can be played online, but it's really quiet.
To answer your first question, if you have friends who are also interested in playing, you could have a TCP/IP game or venture into Open Battle.net. Open Bnet however, has plenty of hacks and edited characters with items that wouldn't appear on an entire character, let alone on a single item. However, if you play private games there, I would imagine you could skip that problem all together. On Single player, there is a program or two that would allow you to mule between characters if you would prefer to play that way. (As Justin stated, it's for those who would like to avoid the fuss of people and internet problems)
On closed Battle.net, the cheating is kept at a minimum, and by joining public games, you can see about joining in groups. Some of those folks might be great to keep in contact with. Adbots are, however out of control on battle.net and can be quite annoying when during the first five minutes, you can't see your map because there's a wall text advertising for six different item sites. On the other hand, there are perks to joining public games if you don't have many contacts and meet a few people who don't mind helping out.
There's another aspect. Ladder vs. Nonladder. Ladder is a semi-competetive environment in that there's ranks for whoever grinds the most xp. Ladder also has a few items, cube recipes and runewords that aren't available anywhere else. Every so often, the ladder gets reset and the characters have their "Ladder Character" tag removed. They still get to keep their items, but they can't make any more new "Ladder Only" runewords etc. You make a new Ladder character (or characters) and start again.
Honestly, you don't lose much by playing ladder of you go on Closed Battle.net.|||The most important aspect of playing online is TRADING. You can find something pretty worthless to you, for example: you play with a paladin and you find The Oculus, a weapon that only the sorceress can use. Now you dont throw it away as in single games, you trade it for a Spirit runeword made in a paladin-only shield !
Also, in online games you can beat higher difficulties (nightmare and hell difficulties) alot more easily.
And is cool to have a party.|||The other most important difference between Single Player and Online (Closed Battle.net) is that Close Battle.net allows the Pandemonium Event, or better known as, "Uber". And in Closed Battle.net, Uber Diable spawns (Diablo Clone). Those are probably the most sought after features. If you want an in-depth explanation of what Ubers and the Diablo Clone are, ask someone else.
~Hazzar