When I create a new software project, I often create a folder structure to hold components that I intend to write later. Sometimes thes folders are empty in early iterations - a reminder to me and others of where things should go.
This presents a problem when working with git source control. Empty folders are ignored by git, so they never make their way into the source control system.
The solution is to add a file to the folder, so it is no longer empty. Many people will add an empty text file named ".gitkeep". If a folder contains any file (even an empty one), git will not ignore it.
Technically this is a hack, but it's common enough that we can think of it as a psuedo-standard. Naming the file ".gitkeep" lets people know the purpose of this file and that it can be removed when useful files are added to the folder.