A phase is a stage, such as online, offline, protected, or unprotected, in a document or record's lifecycle.
A retention policy can contain a single phase (simple policy) or multiple phases (advanced policy). A phase contains paths. These paths, together with the details you set for them, determine when a document or record enters the phase of the policy.
Phases are sequential. To move to the next phase in a policy, a document or record must meet the current phase conditions. You can designate a phase as "protected." While documents and records are in a protected phase, you cannot modify or delete the documents or records. By default, phases are unprotected.