I think this is good advice from Silvestar Bistrović:
An enabling selector is what I call a selector that does a job without disabling the particular rule.
The classic example is applying
margin to everything, only to have to remove …
Josh Comeau covers the concept of margin collapsing:
This idea might sound simple, but if you’ve been writing CSS for a while, you’ve almost certainly been surprised when margins either don’t collapse, or they collapse in weird and unexpected ways.