Leatherworking is often seen as the "light armor" equivalent of the blacksmith. While a part of that is true, the items and equipment that leather can be used to produce goes above and beyond. Leatherworkers can make items like backpacks, belts, waterskins, quivers, ammo pouches, and so on. Items that many adventures would consider essential during their adventuring.
Leather is easy to acquire as one can harvest it from slain beasts and monstrosities. Some even hunt dragons for their scales, as they hold special properties leatherworkers can use. A leatherworker is essential if you wish to get the most mileage out of your harvested monsters.
Leatherworking works using Leatherworker’s Tools. Attempting craft items with Leatherworking without these will almost always be made with disadvantage, and proficiency with these allows you to add your proficiency in them to any Leatherworking crafting roll.
Putting that together means that when you would like to make an item, your crafting roll is as follows:
Leatherworking Modifier = your Leatherworker’s Tools proficiency bonus + your Dexterity modifier
For Leatherworking, after you make the crafting roll and succeed, mark your progress on a crafting project. If you succeed, you make 10 Minutes of progress toward the total crafting time (and have completed one of the required checks for making an item). Checks for Leatherworking do not need to be immediately consecutive. Failure means that no progress is made during that time.
Once an item is started, even if no progress is made, the components reserved for that item can only be recovered via salvage. If you fail three times in a row, all progress and materials are lost and can no longer be salvaged.