Unreal Engine 4 contains a four major tools for working with skeletal animations and Skeletal Meshes: The Skeleton Editor, the Skeletal Mesh Editor, the Animation Editor, and the Animation Blueprint Editor. Each of these are accessed by editing an associated asset or by using the four navigation buttons at the top of each animation editor.
The Skeleton Editor is for examining and modifying the Skeleton of a Skeletal Mesh. This is where you'd add Sockets to joints or test how your Skeletal Mesh's joints are rotating.
The Skeletal Mesh Editor is where you can import LOD's or assign default materials to your Skeletal Mesh. It's also where you'll find ways to attach APEX clothing, modify the Skeletal Mesh's bounds, and even assign a specialized Shadow Physics Asset.
The Animation Editor is where you can work with Animation Sequences and other animation assets, such as Blend Spaces and Animation Montages. Here you will create Anim Notifies, work with Pose Assets, adjust compression and timing of Animation Sequences, and build your Animation Montages.
The Animation Blueprint Editor where you will create the rules for when and how your animations are played. Here you'll be able to use complex state machines and different blends to bring your characters to life.
The final Editor is the Physics Editor where you'll create and edit the collision bodies that will be used for your Skeletal Meshes.