This paper gives an overview emergent behaviour and describes a methodology for developing agents that take advantage of emergent behaviour. It also provides an excellent example of how behaviour can emerge in a multi-agent environment.
Emergent behaviour is the result of the interaction of other, usually more simpler, behaviours.
This type of behaviour is usually characterised as being efficient and robust. Often the emergent behaviour would be difficult to program explicitly. Emergent behaviour is that behaviour which is produced by behaviour describable by V2, but which is not itself describable by V2, although it is describable by V1. While emergent behaviour is very desirable it can be difficult to build upon it and use it in new behaviours. Say the emergent behaviour is walking.