There are three main components to the Mediasite system within Blackboard.
MyMediasite: This is your own personal video management portal. MyMediasite is the place where you can create content, view analytics, edit videos, add quizzes, and organize your content into Channels. It is really easy to record your screen using the capture application Mediasite Mosaic, upload videos created elsewhere, and even add links to external videos that exist in YouTube and Vimeo. Your video content in MyMediasite follows you, no matter which course you launch MyMediasite from.
Mediasite Content: To guide your students through a course in a linear fashion (eg. Read this, watch this video, do this activity), it is easy to add individual presentations or a channel to a course content page for your students to view.
Mediasite Videos: If your course design is better suited for a central library for all videos related to a course, you can use the Mediasite Videos option. It is as simple as tagging the videos with your course module.
In either case, only the students enrolled in your course will have access to these videos.