The Voxel Plugin allows to create fully volumetric and entirely destructible terrains in Unreal Engine.
There are 2 versions available: a free one, and a paid one. This documentation covers all the features of the paid version. If you’re using the free version, you can still use this doc, however not everything will work.
Feel free to create issues/pull requests on the documentation repo (Edit On Github on the top right of the page) if you find spelling errors, outdated docs, poorly written parts, or if you have a question/suggestion.