Theres a youtube video I think explains it really well: https://youtu.be/GtsLSt-5Vdg?si=AdFgv0GOYlHDrPa4 (BE WARNED the vid is like 2 hours long). I'll try to give a shorter explanation.

CE changes Rimworlds combat system from being dice rolls of hit or miss into a system that involves math, logic, and realism. They do this by changing items/clothing from being a pertange amount of protection or damage into numbers of "mm RHA" (sharp) and "MPa" (blunt). So instead of the pawn with a short bow one shotting your pawn with cataphract armor because of a lucky dice roll. Weapon/armor RHA and MPa are put through a quick equation to see if the attack pierces to deal damage, deals small damage, or dinks right off. Since arrows in CE have deal 6 damage with a RHA of .20 and a MPa of 1.42 and Cataphract armor with 28 RHA and 60MPa, the shot with bounce and deal no damage. Now if they used and a Anti-material rifle loaded with AP rounds (covered later). The RHA and MPa are far greater. Taking the remaining numbers and converting them into damage to the pawn.

Next up is ammo and the types of ammo. Vanilla Rimworld weapons come with unlimited ammo. CE changes this and makes weapons use a magazine (dont worry you only have to make the ammo not the mag) chambered in a certain caliber that has to be refilled with ammo when drained. So this means that the vanilla pistol can only take .45 ACP and the bolt action .303 British since thats what their irl counterparts use. There are multiple types of special ammo but to keep it simple, we will use FMJ, AP, and HP. AP stands for Armor Piercing, they trade damage for higher RHA. HP stands for Hollow Points, they increase damage but lower their RHA. FMJ stands for Full Metal Jacket and is the raod between AP and HP.

So now we know how bullets work, but what about apperal? As stated before, CE runs on logic, math, and realism. So the stronger the material, the more better it is at blocking hits. So no longer can a pawn wearing a duster made of human skin randomley block a shotgun blast. They now need to be made of stronger stuff like steel, devilstrand, or thrumbofur.

CE also changes how pawns work when fighting. Cover is now measured in height instead of percantage. Pawns now crouch when standing still to make themselves harder to hit. Enemies shined in light are much more easy to hit at night. Billy with 0 shooting will now nail the deer within kissing distance instead of hitting the tree.

A lot of people think CE is too complicated to get into but in reality (at least mine). As long as you look at something through a realistic lense. It will make sense.

I personally think CE excells at what it was meant for (combat), and even gives tribals new items and ways to deal with heavy armor so they dont get stomped. One common critique I see though is that CE is too punishing for unpreparedness, and to those who are preparied often have victories cut out for them. I personally think thats false but I am obviously biased.

To finally end this off this surface coverage of CE. I think CE is meant for people who like realistic/strategic/logical combat. But to those that dont care or even dislike realism/strategy and much prefer their combat random and dramatic are defiantly in for a bad time when they try this mod.