There is a lot of information about the two different releases available here. The biggest difference between the two in an enterprise environment is that there are some group policy controls that only work in the Firefox ESR version.

Also, the ESR gets security updates but the base functions of Firefox ESR aren't updated as often. This can be good if your organization is running custom Firefox extensions or software that pairs with Firefox. This decreases the amount of updates that you will need to do on custom software and prevents compatibility issues caused by updates.

Thanks for the info. However I see nothing on the page you reference that discusses Firefox RR. Is Firefox RR the same as standard Firefox?

Yes, sorry I should have specified that. RR stands for rapid release, which is the standard build of Firefox.

https://wiki.mozilla.org/RapidRelease

Rapid Release is a term that started as of Firefox 5.0 and on for Releases that you download from www.mozilla.org/firefox/all/

The Releases before used to often take forever to come out as Firefox 4.0 for example had delays for over a year. It was pretty common to have two if not even three versions of Release branches in overlap of still getting updates to complicate things.

Mozilla wanted to put a stop to these delays and have much better control of what went in and the schedule.

Releases are only supported until the next major Release. For example the current 60.0.x Release will be made EOL when 61.0 is Released. The 60.0 ESR however will continue to be supported with a update to 60.1.0esr then. The legacy 52 ESR will have last major update 52.9.0esr on June 26 (along with 61.0 and 60.1.0esr) and then 52 ESR will be EOL on Sept 5 (with no more updates) when 62.0 is Released along with 60.2.0esr.

ESR in general gets eight major updates and when a security and or allowed stability fix(es) is needed there may be one or more minor update for that major update if need be. The 52 ESR will have nine major updates because the current ESR is being based on 60.0 Release and not 59.0.

ESR was made for Enterprise users in mind as they generally did not like to test and deploy major Releases so often. The ESR is focused on stability and not new features.

ESR was based on the 10.0, 17.0, 24.0, 31.0 38.0, 45.0, 52.0 and now 60.0 Releases.

https://www.mozilla.org/firefox/releases/