Can you explain what is meant by a 'snapshot' in a database management system?

In database management systems (DBMS), a "snapshot" refers to the state of the database at a specific point in time. This allows for transaction isolation and data consistency.

A snapshot captures data as it appeared at the start of a transaction, even if other transactions make changes during that time. Thus, a transaction works with a consistent set of data, not seeing intermediate changes.

Example: if a transaction reads data from a table, it sees exactly the snapshot that was present at its start, even if other transactions have already updated that data.