What is the purpose of the extension method CreatePerOwinContext in OWIN implementation by Microsoft

I am a newbie in ASP.NET, and currently learning ASP.NET Identity. I know it’s built on top of OWIN implementation by Microsoft, and I am also still learning that too. So, I came across the extension method CreatePerOwinContext in the Owin startup code, and I don’t see a clear purpose of using it. Is it some kind of dependency injection container? What is the real purpose of the method? In what case it should be applied?