Peer-to-peer and peer-to-X open a new world of transactions in the electricity sector. This world is characterised by the active involvement of new players, both small in size and non-professional in nature, and by new combinations of the activities carried out behind and in front of the meter. Peer-to-peer refers to transactions in which both the seller and the buyer are small in size and non-professional, whereas peer-to-X refers to transactions where only the seller is small and non-professional while the buyer is a different type of actor. Observations from the world of practice reveal the existence of multiple forms of peer-to-peer and peer-to-X transactions. The first part of this contribution illustrates those variants, by providing a sample of concrete implementation cases coming from liberalised electricity systems. The review shows the importance of three components that are essential to the functioning of this new world of transactions and which are discussed in the second part of the contribution. They are: a) the transaction loop, as small players cannot sell or buy from other peers so easily; b) the pricing mechanism, as existing wholesale and retail markets exert pressure on incentives for activating peers; and c) the delivery loop, as peers must deliver via existing grids and system operators, except when trading entirely within private networks.