That's the beautiful simplicity of it. Whether by phone, by Web, by Twitter app, or by the plain old Twitter home page, Twitter is just a single silo of tweets. The gross complexity of it is that it's also a billion random tiny conversations that can be categorized, searched, hash-tagged, nested (on Tweetboards), replied to, sent privately and directly, posted for all the world to see, linked through, linked to, deleted, and retweeted (RT). It is equal parts organized and chaotic.
It's like a party where all the Jesus people, atheists, anal-retentives, pack rats, control freaks, free-thinking hippies, slobs, nerds, geeks, preps, righteous dudes, Ferris lovers, school administrators, Scrabble lovers, Harley riders, sellers, buyers, poets, dreamers, hummers, and screamers are all invited. You can get advice, inspiration, laughs, alerts, pictures, stories, summaries, games, tech news, good news, bad news, fake news, and stuff you didn't know about Argentinian airlines.
Or, you can just check in on how your friends are doing.
This is a big revelation, especially for Facebook users who try to read all their friends' updates and are expecting more of the same from Twitter. Like any place where conversations are being held, you can listen in, speak up, and/or ignore to your heart's content. You can catch up on practically any thread you please, but you needn't.
On the other hand, if you are planning on revealing the deepest, most guarded treasures of your very soul to everyone you hold dear as a kindred spirit . . . Twitter might not be the way to go. I mean, feel free to tweet your heart out, but recognize that you're probably talking with only those people who are listening at the time; you can't expect everyone who has ever heard your voice to hang on your every word.
Still, the twitting and tweeting has more permanence than a normal chat at a dinner party. People in Iran can actually hear you talking about Iran. You can selectively eavesdrop on almost anything. You can bend your ear toward whatever whispers you want.
But when it comes right down to it, it's just a lot of people talking.