Event sourcing is a design pattern used in applications where changes are stored as an immutable sequence of events rather than in a traditional data model. The append-only event log serves as a single source of truth from which the current state of the system can be derived.
By storing the changes as an immutable log of events, you can compute the current state of the system as well as its state at any point in the past. This pattern is useful in applications where you need to keep full track of the history such as in accounting, banking, and e-commerce applications.
Good luck with your event-sourced applications!