An Intro Video is a short clip between 10-15 seconds that play before a longer video.
Think of the roaring lion for MGM Studios.
This helps to create a consistent image and brand on every video you publish. Another benefit is that it creates a short buffer to start the video. Take a minute to look at my first 9 videos and you will see that each one starts immediately with me looking into the camera and talking. The effect is abrupt and I'll be honest a little unnerving. The Intro Video in this case helps to create a smoother transition with the viewer.
With that said, please watch the YouTube video below. Pull up a second monitor to follow along and learn about a pretty awesome piece of free software from Blender.org.
I think you'll be ...