@billbennett @yogthos commit is 1 change to the code
dev is the 1st environment (just a computer) you deploy to check if it works.
Large orgs will also deploy to TEST, STAGE... to check if it works two more times. (at one shop I was at there were like 6 environments to cascade thru & test at each)
Finally you deploy to prod the *real app everyone uses* & you find out there was something different about prod than all lower environments and you're up until late trying to fix it & everyone is mad.