There are different kinds of conferences: there's the "holiday" conference

, the "specific topic" conference and the general and often prestigeous conferences in a certain field.
At a conference, you do several things:
- you meet people. It seems that that is about the most important aspect of a conference. You network.
- you give some visibility to your work.
- you learn about what's going on in the field
- you try to have a good time.
The "holiday" conference is the kind of conference in an exotic place which has in fact not much to do with what you are doing, but you managed to convince your boss that your presence there was important
The "specific topic" conference is usually a rather small workshop on the very topic you're working on. These are IMO the most interesting conferences: 1) you understand normally about everything which is said by others, 2) others are interested in what you have to say, and 3) you can get into contact with people who are working on similar things than you are. The downside usually is that it is "small scale", no prestigeous proceedings (worthless as publication medium to crank up your citation index) and often in not so fancy environment (some hotel in the middle of farmland in a rainy country

)
The general conference is a thing you should go to regularly, every few years. If you can present your work there, all the better (but it's difficult to get a slot if you're not a hot shot in the field). It is great to get an overview of what's going on in the field. The downside is that often, you do not understand 60% of what's being said (it being things outside of your daily activities). It's usually in a prestigeous place. Sometimes it gets into the news on tv. The proceedings are an interesting publishing medium ; often there is an agreement with a journal to publish the contributed articles.
Often you meet former professors and old acquaintances. There are usually also nice activities and dinners. Don't forget your smoking
