dKH and dGh Confused

I have always been confused with the following,

Alkalinity is equal to general hardness? And to fish and plants how
important is general hardness?
When people talk about buffering capacity they are talking about dKH, right?
When people talk about not having enough buffering capacity or too much
buffering, they are talking about carbonate hardness, dKH?
When a PH up or PH down kit bounces and gets to the same reading after a few
days, is this too much buffering capacity?

Please advise.


thanks.