Understanding the significance of Change Document Number

Hi Experts,

Although it has been stated multiple times in SAP Documentation for Change Documents as :

"The change number is not the same as the change document number. The change document number is automatically assigned by the function modules of the function group SCD0 when a change document is created for a change document object. It uses the NUMBER_RANGE object "CHANGEDOCU".

The change number is assigned when changes are planned by the user. The same change number can be used for different change document objects."

But I am still not able to understand the change document number.

I tried looking at CDPOS and CDHDR but Change Document Number is not present in either of them. All I can find is the object id and Change Number.

In transaction SCDO also I am not able to see anything related to Change Document Number.

Now I am having the following questions:

1.) What is a change document number?

2.) What is the significance of a change document number? Where it gets used?

3.) Which table/transaction stores Change Document Number?

Please help me out.

Thanks,

Partish