It's actually pretty easy.
DAV ("Distributed Authoring and Versioning") is basically a way to share content between people in a central source. WebDAV is that applied over the internet. It's an older protocol but quite powerful - full CRUD support, plus fancier features like locking.
Windows, and probably Linux too, has built-in support for mounting WebDAV endpoints as "network locations" or virtual drives (eg, Z:). With full DAV support, you can edit files over the internet. There are three different levels/classes of support:
- Original WebDAV (RFC 2518)