@AnnaLoo91 - Until this version became available at the end of Oct 2020, TS3 was 32-bit only across the board. What that means is that on Windows (which is still the case) the game cannot use more than just short of 4 GB of RAM no matter how much the player has to work with. The 32-bit Mac version of the game can only use 2 GB. This is very limiting to gameplay. Further, Macs running what are now the two most recent operating systems, Catalina and Big Sur, cannot run the 32-bit version at all thus locking these players out of the game entirely.
The new 64-bit Mac version removes the RAM limit and will run on the two most recent Mac systems. As you have probably read by now, it brings a lot of gameplay and, on some hardware sets, stability issues to the table that aren't there for anyone else, though.
If you do not have a Mac capable of running the Metal API (tell us the specs under Apple Menu > About This Mac if you aren't sure), or do not have a Mac in the first place, then you aren't missing anything! It would be great if we had a 64-bit version for Windows to work with that is stable and does not bring the other in-game issues into play, and who knows maybe we will someday, but right now this doesn't exist.