The customizer is used to customize the appearance of the page. Appearance tools can be found in the administration of your website under Appearance ›Customize .
Customizer and its functions
In the Customizer, you customize the appearance of the theme, page layout, menus, widgets, header, colors used, font, and so on.
When editing, the Customizer tools available to you appear on the left. You can see all the changes you have made in the live view on the right side of the screen.
You can also see how the changes will take effect when the page is viewed in full screen, as seen by its visitors. To view in full screen, click Hide panel in the lower left corner of the menu. In addition to this option, you can also choose a sample of the page on mobile devices.