Shared folder inside of each Plato theme directory contains by default 2 MVC / Razor based layout files. These layout files allow you to customise both the front-end and administrator layouts.
For example you can modify layout files to...
TIP The Plato layout files are regular MVC layout files so can include Razor code, tag helpers, view components or partial views to ease theme development. If you use your own code or views remember to add your import or using statements via the _ViewImports.cshtml file.