Understanding Related Aggregates in Domain-Driven Design

Within the community, there is been an ongoing discussion about the aggregate pattern. From Eric Evans perspective it is:

An architectural pattern that enforces the consistency of a set of interrelated constraints, by defining a transactional boundary, a concurrency boundary, and a distribution boundary.

A lot of people seem to have different perceptions, different explanations or altogether don't think we need to use the pattern. In this #VDDD meetup, Thomas Ploch will tell us his vision and after we will open the dialogue and try to make more explicit: What is an aggregate and how do we teach this to other people.