I mean, I can read them, but I want to know what they really mean. I did some googling to try and figure out what both of these red ones correlate to but I can't find anything and I want to know if it correlates to a specific issue or part or whatever. The reason I ask is because I had a new catalytic converter installed this month, but just the one closest to the rear. The one closer to the front is one of those cheap 48 state legal ones that my dad had installed a while ago, so I'm wondering if the old cheap cat might be causing problems. Especially since I need to renew the registration soon and I live in an area that does emissions testing. Hopefully this is written clear enough and I don't just sound like a lunatic.

These are mode 06 readings. it just shows Tid (ecu) CID component. Basically the internal values of the écu monitoring component voltage and if they are out of spec set a CEL. What codes if any do you have? you should have a scanner that can decipher this data into english.
What year 4runner? What issues?

Do'you have p0141 code or pending?
Edi :'the écu is monitoring the voltage from the o2 sensor and the acceptable to pass is .032v but it's getting .056 volts so it is out of spec hence there should be a code.
Best I could do.

It's a 2002. I just cleared the ECU today after fixing an exhaust leak that was giving me p0136 and drove it around some so no codes just yet. I've been slowly playing whack a mole with this thing, new problems pop up after I fix a different one! So recently I've been driving trying to set CEL's. Will drive more tomorrow to see if I get a code. In case it matters the rear O2 sensor is brand new, it was just an exhaust leak where the new cat was welded in.

Edit: Only just realized how it might be a little stupid trying to find a problem when there's no codes yet...

P0136 is usually caused by the rear post cat 02 sensor. The exhaust leak might have been the cause.

So my takeaway from this is that PIDs are not a magic tool that can tell you anything you want to know, it's just computer numbers. Honestly my assumption was that I could use them in troubleshooting if anything came up. I shouldn't have been so confident!

I have never used them but for those that understand the mode 06 code'system there is plenty of insight in diagnosing problems.

PIDs can be very useful in helping spot an issue, but they are not a magic bullet. You need to have decent amount of familiarity on what the ECM is actually doing when it records those numbers.

From what info I could find from you screenshot, this may indicate an issue with your evap system.

from: http://alflash.com.ua/OBDII/PIDs.pdf
The service manual says on page DI-77:
Have you gotten any DTCs? They will take two trips to set a Check engine light, but you should be able to find them in pending after only 1 trip.