I think this video is an excellent primer for BlueMix. Platforms like BlueMix take care of a lot of the manual steps of setting up a server including infrastructure, devops, and runtime administration for scaling your applications. It really is a one stop shop for developing applications in the cloud.
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It’s also been around for a while. I think it’s one of the earliest Bluemix videos that was produced.
That video was new in February of this year. I think they replaced the original one with this one.