To collaborate on an Unreal Engine project, you cannot use a Dropbox or a NAS. You need source control to synchronize your files with your team using a central server. Learn more about collaboration in Unreal Engine.
You can either use the Unreal Engine source control plugin, which unfortunately slows down the engine, or a desktop application like Anchorpoint. Here is a tutorial on how to use Git with Azure DevOps for Unreal Engine projects.
Version control (or source control) is a way to collaborate on projects. It's a different way of tracking changes than incremental commits, and it helps you keep track of your project and distribute your files.
Git is an open source source control system and the most popular system in software development. It is required to make collaboration in Unreal or Unity work, because you cannot use a Dropbox, GDrive etc. here. Git (or most version control systems) are very complicated for artists. Anchorpoint makes it easy to use Git for them, because it limits the functionality to a 3 button solution.
Git LFS (large file storage) is an addon for Git to manage binary files. Game projects have a lot of binary files and require Git LFS. Without it, your repository will quickly reach it’s limits in terms of performance and capacity. Technically Git LFS performs storage operations to store and transfer your files efficiently.