[Gimp-user] what does the 'Link to brush default' toggle button ?

[Cristian Secară <liste secarica ro>]

On the brush panel, at the right side of every slider, there are two buttons: a single click button with the 
tooltip 'Reset [something] to brush's native [something]' (this one is ok) and a toggle button with the 
tooltip 'Link to brush default'.

Question: what is the purpose of this 'Link to brush default' ? I don't know where to look for a difference 
when I do something with that button pressed or released and I am also unable to find a description for its 
real usage.

Thank you,
Cristi

-- 
Cristian Secară
https://www.secarica.ro