Hi Fabian,
e-participation is a bit of a broadbrush term for describing any way of engaging people online in an active community- whether it be simply to vote on an issue- say on a change to your local rubbish collection service, or to join in a conversation, say on the impact of nanotechnology on society. It is used particularly in the context of say public participation in services.
If you're interested in finding out more check out
E-participation for a good list of links...