A MINISITE is a special Layout that can have its own menus and Design Theme. A project is the same thing without any of these pre-installed.
Give the Minisite an avatar [visible in listings] by uploading an image named avatar.png to the Minisite Root.
Give the Minisite a custom logo or banner by uploading an image named logo.png to the Minisite Root.
Set a Layout preference via More Actions [1] > Layout [2].
Add extra Layout elements [3].
Install a Design Theme via More Actions > Design [4].
Add a Menu, Sidebar or Footer via Actions > New Site Element [5].
Add a Header / Sticky via the New Sticky Action [6].
Import a Personal Site: merge with an old-style Intranet Personal Site by adding the User Name of the Personal Site as a byline under [3].