Desertlands mod gives your world a new biome or environment to explore and gather items from. From its name, this is a desert-themed biome which you can travel to by defeating Husks and collecting a GoldOrb, and finally, crafting a portal using sandstones which somewhat resembles a nether portal.
You will then use the GoldOrb to access this area.
This new region offers a lot of new resources on Desertlands to collect as well which can be used to craft new items. You will also encounter new mobs and biomes along the way.
It also has its own village complete with residents.