1. Unearthed Gear
Up until now you were able to find Charms that were unearthed. Each was random and had different stats and abilities. They are now adding actual armor and weapons to that system. One neat new thing is that each new gear you unearth (by mining, rewards, etc.) will look slightly different. For example, they showed Rathalos armor that looked slightly different). You can find the same piece of armor or weapon, but with slightly different appearances, stats (like higher attack, an additional slot, higher rarity, etc.). The rarity works like charms, there stuff like rusted or weathered armor, etc.
4Gamer added that you can find gear for monsters that are not even in this game!
2. Unknown Forest
The forest is for single player free hunting, like Moga Forest was in MH3U. However each time you go there, the area is different. The structures, the items you can find or mine for, the monsters that appear there, etc. are random. You can find the Unearthed Gear (mentioned above) in the forest.
3. Guild Quests
The most efficient way to find the best materials and items in the Unknown Forest is through Guild Quests. These are not quests that just exist like normal quests. When you go into the forest and hunt the monsters that are in there and mine the items that can be found, you receive a rating based on your efforts. When you leave the forest, if your rating was high enough, you can save that excursion as a quest, forever locking in the items/monsters/etc. that were there that specific time. You can then replay that quest, or share it with other players (friends, or though streetpass).
For the excursions you save as quests you can play them either single player or even with friends. As you clear Guild Quests the level of difficulty/rarity of the things you might encounter goes up. Higher level Guild Quests means a better chance to meet stronger monsters, and get better items. A Guild Quest lists info like if there is a ‘treasure area’, poogies, and what the tendency is for what kind of items you might find/get (lists both tendency for weapon and armor).
