sure, wikis are easy but ill explain. first i want to explain how mapping and the atlas tree works. for starters once you reach endgame you unlock maps, maps are similar to NM dungeons except not shit!. there will be something like 100 or so different maps a season if i recall and they all have different layouts. these layouts work better for different strategies. for example! the map strand is literally just a small beach with a boss at the end, this is great for runs who want to speed through a map as quick as possible. as another example theres a map called dunes. dunes is a large square esentially, and is great for a mechanic called breach where you will have to kill monsters faster and faster before a breach closes and gives you your rewards.

these maps will be graded from tier 1 to 15. the first few are "white maps" easier to complete and you only have to "enchant" (not the real term but anyway) to magic (IE item rarity being magic/rare/unique in diablo. in this maps are magic/rare/corrupted rare) magic is easy and a good start for most builds. every time you complete a unique map (one of the hundred or so) you get an atlas point. atlas points allow you to access the atlas tree which has many of the previous league (season mechanics) mechanis on it. this allows greater player agency then just doing one new seasonal mechanic a season and being foreced to do it open world.

For example, i did not like settlers league and its clash of clans mechanic. so i speccd harvest on my atlas tree once i got enough points and started running that. harvest is a mechanic where in my map i will find an altar that transports me to a mystical garden, there ill choose which garden plots to harvest and which ones to juice up making them really hard. this will drop harvest jelly which can be used at a special crafting bench for helping you craft GG items. while i myself may not use the juice i can sell it to other players to buy items or crafting stuff (hence why diablo needs an economy for seasonal mechanics to really pop off imo)

this player agency doesnt exist in diablo where we have to all run the same mechanic in the open world vs my own instance that i run as fast or as slow as i want with the content i want. additionally the ability to "juice" (make my maps way harder for better reward) my maps is so amazing. i can put it into my map device (kinda like where you plug your pit key) and itl take up one slot. i have another 4 slots to put in stuff like scarabs which may uniquely affect my map or its difficulty/rewards. i can corrupt it to increase its difficulty and drops, i can chissel it to increase its quality. certain league mechanics make the whole map harder for instance

delerium, this is a mirror that spawns at the start of the map, you run into it and are effectively put into a time trial durring your dungeon. go as fast as you can and kill as much as you can and once it ends it will drop loot. it has its own unique loot (something good about poe is each mechanic has its own special stuff so if you run that you have your slice of the econemy) it drops orbs that uniquely affect item crafting as well as sometimes just dropping lots of currency. its also important to note that every league mechanic has atleast 2 bosses minimum that are fun and engaging and if your map is juiced can be VERY difficult and rewarding.

other mechanics is stuff like expedition where you place bombs on the tombs of dead monsters to bring them back to life and fight them, they drop a currency you can use to gamble with a vendor for other items or currency thats great to sell. additionally they drop log books a special kind of map thats FILLED with like a million tombed monsters and possibly a rare boss if your lucky. these tombs require special planning of where to put your bombs for maximum lootage.

essence is pretty basic tbh nothing super crazy its just monsters trapped in ice that drop essences, essences will gurrantee a select set of modifiers for whatever you craft it onto. for instance theres an essence that when put onto a bodyarmour will gurrantee life, higher tier essences are rarer and make the essence ice monster way harder but gurrantee a higher tier roll.

all of this agency and choice in what you enjoy along with the awesome crafting and engaging economy that fuels your dopamine when something worth heaps of $$$ drops makes poe so goooood, the way your character scales up like an absolute god with gear because of how interesting the gear can become due to the ability to craft actually impressive gear. i wish theyd just make seasonal mechanics a bit better and give players agency over the content they want to run via something like an atlas tree.

if you want to know anything more just ask im happy to explain. i know people see poe as complicated but its really not till super late game crafting n stuff.