Someone posted a similar question earlier :) , but basically clicker training is a type of training based on conditioning the dog to the sound of the click, and using this as a marker for the exact second the dog does the correct thing. The dog then gets a reward and eventually when the dog understands the behaviour required, a vocal cue is added.
The dog is never told off, but is "shaped" and allowed to work out what is wanted. AS an example, I used the clicker to shape the start of a Sendaway to a hedge. I taught, touch stick, then send to stick, then send to stick in hedge, then just send to hedge. It was all easy with a clicker :)
I then started to "up the criteria" and wanted more accuracy. So sent her out, and she lay down - but I waited her out, and she thought a bit, then offered me a down nearer the hedge.. She then got the click so she knew what was required was for her to get closer to the hedge, etc.
I don't know if i am explaining this very well, but I feel it is a very effective method of communication. The dogs love the training and there is absolutely no stress involved for owner or dog. Like any training it may go wrong but then it is up to the trainer to work out what is required, and to communicate this to the dog.
If the dog gets things wrong, and gains experience of this type of training, the trainer can use words such as "Wrong" or "try again" and the dog will respond accordingly :)
It can sound a bit off putting and when i started i didn't like it, and couldnt see the point

But i just needed to practice a bit more and to realise the benefits.
Anyway hth a bit
Lindsay