Unlike a word processor that only allows you to create one document for each piece of writing—and forces you to write linearly—Scrivener can hold multiple documents within a project. Each document can be a scene, section, chapter, blog post, magazine article, or journal entry. The documents are easy to move, categorize, search, save versions of, and edit.
I started using Scrivener when it was still in beta, several years ago. It always amazes me when writers don't use it.
Writing's complicated enough. Scrivener puts you back in control...