Participant (or user) - is a physical person who has an account in the system. Users can exchange goods, services and participate in collective projects. Each participant has an open set of reputational characteristics, which are based on historical data about participant's transactions in the system.
Need - is a description of the goods or services that are needed by any participant, or some number of conventional units.
Offer - a description of the goods or services that may be made by any participant, or number of conventional units which belongs to the participant.
Contract is a key concept of Zero Exchange. Contract binds the needs of participants with the appropriate offers and joins participants together, allowing use the phenomena of division of labor to achieve goals. The contract's lifecycle consists of the following stages: