Tagging layers as image categories for a master image
You can tag layers in an Adobe Illustrator canvas as image categories for a master image. Before you start, ensure that you have selected the canvas that corresponds to the master image.
If you use the Tag Document button while working on an image under an image category that is not associated to any master image, a new master image will be created and the existing image will be added as a layer on the canvas. This layer will be uploaded as a new image in its corresponding image category and is associated to the new master image.