In tracker-less or surface based AR you can place virtual content in your surrounding space. How it works, is that the camera maps the real world into and augmented space and allows you to place digital content and interact with it.
These type of experiences are different from tracker based experiences as they do not require any anchor images and in such experiences you can interact with digital content in your own surroundings rather than over an image.
Such campaigns require you to scan a well-lit but none shiny flat surface to place your digital content. Just scan your surrounding and begin interacting with digital content.