You chart each dungeon floor by walking over the tiles, painting the ground as you go. Events and battles occur on specific tiles, though battle tiles shift locations on the same floor upon revisits. Events can be anything: could be treasure, a bestiary page on a particular monster, various shrines and services, or navigational puzzles to solve; all of it gets recorded in an exhaustive exploration log with the relevant Z/Y/X coordinates so you can find your way back to something should you wish to. Coordination is really important to the game otherwise too because each party member exists somewhere in the labyrinth according to that spatial data--when you swap party members in and out, you have to be on the same tile as them, and those being swapped out get left on the spot. That aspect interacts with the game's design in interesting ways where petrified folks, for example, aren't just a status effect you're lugging around--you have to leave them in the labyrinth until you find a way to heal them, and then go back and retrieve them. Similarly, if you experience a full party wipe, you can form a party of whoever's left topside at the adventuring academy, and they have to make it to the knocked-out people to rescue them--if they perish too and no one's left, then that's some kind of failstate that I haven't seen yet but does exist. There is a lot to the game that emphasizes a playstyle that's not about individuals, but the shifting and flexible currents of managing a guild, where you'll rotate people in and out as needed because something unforeseen will certainly at some point happen. The game also doesn't seem to have manual saving of any sort, instead favouring regular autosaving, so whatever risk you undertake for your curiosity or pushing too deep you will have to commit to.
The battles operate on ATB principles but by default they're set to "wait", and that differs from the FF convention as any ally's turn filling up pauses the game entirely so you can treat the entire thing as a fully turn-based system where you just have a visual tell for all turn orders. Healing in battle is not emphasized, and instead it's about damage mitigation: everyone has physical defense, magical defense and health points, where corresponding damage types exhaust the character or monster's defenses, upon which that damage type can be used to attack their health values and bring them down. You're equipping people according to these needs and coordinations, in having the right kind of tools and damage type spreads to take on the enemies, while being mindful of what you can endure, with hats and clothing increasing the phys/mag defenses of a given character. There's a basically equal spread given to single-target weapons and spells and multi-target equipment in the game's repertoire, and you have to arm people accordingly with other nuances in mind too, like flying enemies needing ranged weaponry, or mages reflecting spells, requiring physical offense. There's a real mathy nature in gauging all the cascading risks in an encounter, trying to take out enemies before their turn fills up, and taking calculated risks with your own options--many of the stronger weapons operate on the damage formula style of FF's axes, where they have a high maximum damage value but could just as easily do as little damage as one point. Otherwise, weapon damage is fixed, so you're supposed to plan around all of it as it happens. It's a dense but intuitive system.
It's just a really interesting mix of exploratory and combat concepts that interact with each other in novel ways you don't get in most other games, or in this specific combination. I want to stress again that it appears at least to me to be about the cohesive whole of the guild's operations, so any hardship experienced along the way should just be taken as interesting texture, even if you have to do something like training an entire roster of recruits from scratch because the previous crew made a miscalculation. That's happened to me, and it was an awesome feeling to get as a real consequence of my actions.