The Exploration Mod,

Which focuses on:

The Exploration dimension

The Exploration is where all of the biomes and other features are located in. You can get some help in progressing there with the Advancements tab (pressing L by default.) You can find new biomes, trees, rocks, ores, mobs and structures there.

Structures

Moon Asteroid

Moon Asteroids spawn everywhere (above ground) in the Exploration Dimension, they are made out of Calcite, Moonstone and Moonite Ore. Moonite can be used to craft armor that reduces the wearer's gravity and extends their safe fall distance.

Biomes

Leaking Woods

Leaking Woods is the biome that is found in the overworld (and also in the Exploration dimension), there you'll find a new wood type, which can also contain Resin, that you can collect by either breaking the block or stripping them with an axe. With Resin, you can make food by smelting it and combining it with sugar, or you can create building blocks for decoration and to build the portal. The biome has it's own ore: Amber, which can be found generated naturally in the underground. Amber can be used to craft Amberlined ingots, simply being a slightly stronger and much more durable version of iron. But Leaking Woods gets dangerous during the night, only having special skeletons as a hostile creature, and even more dangerous during full moons.

The Forest of Eternal Winter

The Forest of Eternal Winter is a cold, snowy biome, with a hostile fauna, being made of only three: Strays, Hush Puppies, Bound Souls and Mama Spiders. Hush Puppies are a new mob, that can only hear, and not see. They spawn above ground in the Forest of Eternal Winter during the night. Bound Soul is a new (unfinished) mob, that flies and fires projectiles towards players. Mama Spider is a big, slow mob that has alot of health, and has a chance of spawning a spider when taking damage, it is found in the caves of under the Forest of Eternal Winter. The biome features its own wood type, rock type and a new ore: Nephrite, which is slightly stronger than diamond.

Alp Lands

Alp Lands is a more overworldly biome, with creepers, zombies and skeletons, and villages! It features scattered spruce trees, a new rock type, Gneiss, and ore type, Hematite. It's pretty flat and makes a good space for building.