For page, we have 2 setting levels: Global settings in Customizer > Page and Local settings for each page when you edit it.

This is page global settings in Customize > Page. Settings here apply to all pages.

Local page settings below page editor, It applies to the current page only.

Global settings will apply to all pages while local settings apply to the current page. Local settings can override the global settings. For instance, if you set sidebar position to be “right” for all pages (global setting) but for the current page, you set it to be “left” then It’ll display sidebar left for the current page.