Question about coldbox.xml and Environments.xml

If someone adds name/value pairs to the Environments.xml file but does
not put them in the coldbox.xml file , and the Environment url
matches , will the variable exist even though it wasn't declared in
the coldbox.xml? To rephrase, does environments.xml create variables
or only override existing variables declared in coldbox.cml

It will create them if they didn’t already exist, or override them if they did.