i was reading about repositories at the official ubuntu documentation , and can't understand the difference between both of them
Close. The 'Close' button must be selected to execute any change(s). If the action would change system files, they are written at this time.
Reload. Any time a setting is changed which alters a repository setting the 'Reload' button should be selected to allow the applicable repository database to be updated. Repository information will not normally be updated until the 'Reload' button is selected. If you do not wish to use 'Reload', select 'Close' to exit without updating the database.
can't understand :
the close action where it states it use close to execute changes and then stating select close to exit without updating
why would it do any changes to the database -without apt-get - other than changing configuration files
-the documentation i read : https://help.ubuntu.com/community/Repositories/Ubuntu
The Close button will save changes in your settings, i.e., in the repositories you have enabled or disabled. It will not, however, go out to the internet and update the package information of these repositories. That is what Reload does.
When closing, "Software & Updates" will also prompt you to reload. Otherwise, your package information may not be up to date. For example, if you add a repository, then closed without reloading, the new repository will be registered, but your system will not yet be informed about the contents of that new repository. To achieve the latter, you need to reload, which required being connected to the internet.