Snapshot is a snapshot of the virtual machine (its file structure and state), which can be used to return the system to the saved configuration at any time.
Sometimes a snapshot is mistakenly attributed to backup technology. Unlike a classic backup, a snapshot does not imply the creation of a full-fledged backup. The snapshot only creates a status log of the virtual machine at a certain point in time.
After the snapshot is created, the system continues to work, but all subsequent changes in it will be reflected only when a new snapshot is created (if any). The log created by a snapshot takes up much less disk space than a full backup, but all the information in it is read-only.
A snapshot is an ideal tool for developers, testers, and anyone else who is experimenting with system configuration and installing updates.