More questions Multi User Data ? How do I define USER ? and DATA?

I am trying to do a boolean on this object. How is it that this object has more than one user? Is part of it in a different collection ? I am thinking I am the USER and there is only one of me so it cant be true that this object has more than one user. I am the only person who uses ?
USER means something is getting something from something else.
I am missing something here. I feel like I am really missing a basic concept with blender. What do I need to study ? OK I will read the Manual. I guess a guy needs to go through the whole manual I suppose. But any advice ?
Thank you

It sounds like your object is a user of a mesh datablock which has multiple users. This happens when, for instance, you press Alt + D instead of Shift + D to duplicate an object. When you do this, the new object references the same mesh data as the old object, so that any change you make object’s mesh data will affect the other object’s mesh data, since they’re the same data. This makes Blender unable to do certain things like apply modifiers.

Duplicate the object with Shift+D and then you should be able to make the changes you want to that new object. Or, in the “Object Data” section of properties window, click on the number of mesh data users next to the mesh name to create a “Single-user copy”.

This is important: The object and the mesh are two different things. Your object can have a different name than the name for the mesh data it uses. See the little dot in the middle of your object when you select it? You may know that as the “Object Origin”. But really, you should think of that dot as the object itself. An object is really just a point in space with location, rotation, and scale values. The faces, edges and vertices are attached to the object, but they are not the object. That is mesh data, and it can be linked or duplicated independently of the object.