Versioning creates a "snapshot" of a page at a specific point in time. With versioning, you can perform the following actions:
- Create a version of a page.
- Restore a page to a previous version in order to undo a change that you made to a page, for example.
- Compare the current version of a page with a previous version with differences in the text and images highlighted.
For more details on each of these three points check the documentation[1]
If you disable the page versioning you will not be able to take the advantages that are mentioned in the above three points. But if you are facing issues like AEM is slow or the performance of AEM instance is not good then you can disable the versioning on the replication agent.
In CRX the versions are stored under the path "/jcr:system/jcr:versionStorage". If you open the jcr:content of any page in CRX like /content/we-retail/us/jcr:content you will notice a property "jcr:versionHistory", when you click on it you will be redirected to the version of the page
On the sites.html UI console if you wish to check the version of a page simply select the page, and open the Timeline from the options tab and will display all the available versions of the page along with other details.
[1] https://docs.adobe.com/content/help/en/experience-manager-65/authoring/siteandpage/working-with-page-versions.html