From Blender version 2.8, 2.9, and 3.0 , Group is known as Collection. When there are many kinds of different objects such as 3D characters, 3D objects, props, lightings, cameras, etc., you can group the objects into one by using Collection, to well-organised the scene in Blender. Below shows the quick tips Blender group object using collection in Blender. Hope this helps. More Blender Tutorial, Tips and Tricks are available here.
How to Group Objects using Collection in Blender
If you would like to Group objects using collection, you can select the objects, then press shortcut “M”.

There 3 options of using Collection to group objects in Blender.
1. New Collection
It will create a new Collection to group objects
2. Scene Collection
It will move the selected objects to Scene Collection
3. Collection
It will move the selected objects to selected Collection
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