Page Layout
PageLayout is used to define page-specific elements across application.
Title
Title is used to render page title in the PageHeader.
MenuItemName
Indicates current selected menu item name. Menu item name should match a unique menu item name defined using the Navigation / Menu system. In this case, it is expected from the theme to make the menu item "active" in the main menu.
Menu item name can be set on runtime too.
Be aware, The Basic Theme currently doesn't support the selected menu item since it is not applicable to the top menu.
BreadCrumbs
BreadCrumbItems are used to render breadcrumbs in the PageHeader.
Toolbar
ToolbarItems are used to render action toolbar items in the PageHeader.
Check out Page Toolbar