Blender Made Easy covers everything you wanted to know about instancing collections in Blender 2.9.
Instancing is a great way to create new content quickly and easily. Unlike UV unwrapping, which can be time-consuming for larger models with many textures or materials applied on top of one another as well as mesh subdivision distances that exceed some limits imposed by your graphics card’s memory limitations (512 MB in most cases), instances allow you work at any size without having those burdensome problems getting in the workflow path!
This new tutorial from the Blender Made Easy channel shows how you can use instancing collections to unique designs pretty quickly. The technique also allows for animating visibility of collection within blender, making your life that much easier!