It saves the history of changes of your items.
You can see all past revisions through the backoffice (click on the little clock icon).

You can probably empty it without problems( you'll just lose history).

Thanks very much. I regularly edit and update posts.

Found the little clock icon Pity under actions there is not an option to delete.

Have truncated table and all seems fine

Thanks again that has halved my database size.

What host limits DB size these days?

It might still be an inconvenience for backups time and especially restore times.
Especially in the case you replicate a production server on a test server.