Versioning is the mechanism that enables multiply versions of the same KB Article.
Only when the article have status Published, versioning support in edit form will be available. In that case at the end of form will appear two checkboxes: Minor change and Major change.
Minor change will add minor step to an article version number, but it will not create a new version of the article. Version number is updated each time you click Save for article in Edit mode (and Minor change is marked). Note that version number is not updated if you add a link to other article, ticket or CI, or if you add an attachment.
Major change will create a new version of the article and all the changes will be saved in that new version. Old version of the article will not be updated and is set to Archieved status. The new version is a new KB Article that replaces the old one. Only Article properties are copied to the new Article. All comments and relations are reset.
For example: if the current article version is 1.0004, minor option will update changes and version number to 1.0005. Major change will create a new instance of the article with version number 2.0000. Old version will still be 1.0004.
Only one version of the same article can be in Published status.