Page templates are specific to each theme you use. They provide modified layout or add a functionality to your pages (such as list of child pages). Certain page templates might even work with posts and custom post types.
If your theme provides some page templates, you will be able to select them in the sidebar on page/post edit screen:
For more information about what page templates your theme provides and what they do, please check your theme documentation.
Page builder template
Are you trying to build your page using a page builder plugin?
Does the layout look odd, narrow or padded?
Your theme might contain a dedicated page template for use with a page builder. Please check your theme documentation for more info about this and how to set up the layout for this page template.
If your theme provides you with “Page builder” page template, don’t forget to assign it before enabling your page builder plugin on that page:
