A DOI is useful feature to any electronic document. What the ID number in your passport is to you is the DOI to a document. It simply helps to make sure you address the “object” you want to address.
Similarly, there may exists several “Joachims Zwiwwelkoecks” in this world (well, it may or may not be the case). However, if any of this person gets his (or her) unique ID (could by a simple number), then we would in principle always be certain that we address the right person.
Same idea for DOIs.
Making Github hosted blogs reproducible using DOIs
Blogs may suffer from the problem that they may vanish or change content from one instant to another.
One solution to this problem is using DOIs and Github. On Github, one may make a “release” of a repository, that’s some kind of snapshot of the state of affairs of your project. This snapshot is saved as a zip file and can be downloaded by anybody - thus documenting the state of affairs at the given time. Zenodo offers the feature to provide a DOI to a Github repository.
Learn more about the “howto” here.