The Sims 4 Outdoor Retreat is the first Game Pack in the franchise. It sets a precedent that minor add-ons for the game will include gameplay features, as opposed to objects and clothing via Stuff Packs.
Outdoor Retreat's Herbalism Skill relies on 10 new Herbs and some of the new insects that can be collected. The Skill allows your Sim to make potions and salves that heal ailments like bug bites and calm emotions like anger, while also producing excellent Fertilizer for your Garden and weed repellent. Visit the linked Guide to see more about this Skill, which is as fully featured as others, just difficult to use heavily because of the ingredient requirements. You can take Herbs you collect back home to grow and use in practicing it, but will sometimes need insects in order to complete a recipe.
New Aspiration: Outdoor Enthusiast
The game pack's new Aspiration is tied in with the new content. You'll have to harvest Herbs, catch fish, level Herbalism, collect Insects, sleep 5 nights in a tent, and befriend the Hermit of Granite Falls, who resides in the Deep Woods. Its Reward Trait is Survivalist, which makes Sims happier when camping (even at home) and enjoying the great outdoors.