Joe,
Just about all you'll ever need (ok, not really but close

) or want to know about the 80 series or LX can be found here:
80 Series FAQs
It is a sticky at the top of the 80s section.
Within that you will find links for just about everything from what all the crazy abbreviations mean that people use to the 80 series buying guide to rebuilding a transmission.
You'll also find a section on how to determine if the 80 had factory installed
lockers in chapter 1 to write ups on the basics on differentials in chapter 2.
You can spend days reading everything and I suggest that at the very least you glance through the majority of the FAQs just so you know what is in there - like the section about starting problems should that ever happen to you.
I see on FJ60's there is a rear locker switch on the r/s of the steering wheel. On the FJ 80's early 90's there is a center Diff Lock on the r/s and a dial on the left.
Can there be one without the other?
Where are they on the mid-late 90's?
Also what does the center locker do??? I am puzzled. Is it a release of the Full-Time 4WD?
Couple quick notes. The FJ80s IIRC all had a CDL switch installed. '93-'97 FZJ80s did not have a CDL switch installed as a standard. (Read the newbie guide on the differences between FJ80s and FZJ80s because there are some pretty big differences). You can easily add a CDL to a '93-'97 FZJ80 as the harness and connector are there, it just takes a switch (whether you choose the real CDL switch or the cheaper hazard switch route).
The lockers (factory) utilize the rotary dial to the left of the steering wheel and yes, you can have one without the other. Many folks add the CDL switch as there are benefits to doing so like being able to lock your center diff in high or if you do the pin 7 mod you can have the center diff unlocked in low (helps with turning radius on tight trails when in low).
As for what the CDL does. The 80 series is an AWD vehicle. The CDL locks the center diff basically changing the AWD behavior of the 80 into a 4WD behavior (i.e. the front and rear axles are 'locked' together and getting equal power like in a regular 4WD vehicle). There is no provision for an 80 series to release the AWD or full time 4WD functionality other than going with a
part-time kit that changes out the front hubs for selectable hubs plus some changes in the center diff/transfer case.
Another thing the CDL does is if you ever need to, you can remove a drive shaft (front or rear), lock the center diff, and still be able to drive the truck. If you remove a drive shaft and don't lock the center diff the truck will go no where. Think of it along the lines of an open diff where one wheel gets lifted off the ground and all the power goes to that wheel with the least resistance.
HTH and welcome

(official MUD welcome)