What are commitments?

To assist with total order determination of events, nodes declare to the network a periodic commitment of all events they have seen.

This commitment is produced either when a node takes part in Temporal Provisioning for an event, or at will over an arbitrary interval.  A commitment is a Merkle Hash constructed from the events a node has witnessed since submitting a previous commitment, with the first leaf being the last commitment a node submitted, producing a linked sequence of commitments over time.

For more information, see: https://papers.radixdlt.com/tempo/#commitments