What does it do?
First it will check if an objects exist based on a set of parameters (like primary key or slug). It Django can't find the object in the database, it will create the object for you.
An example
def post_detail(request, post_id):
post, created = Post.objects.get_or_create(pk=post_id)
print(created)
return render(request, 'template.html')
You probably noticed that I have to variables in front of the function call. This is because "get_or_create" actually returns a tuple.
The tuple contains the object + a boolean variable telling you if the object was created or not.
If you visit a post for the first time, the object will be created in the database, but the next time you visit the same page, Django will get it from the database instead.