On July 2, Youtube announced a new feature related to their captions, an interactive captions viewer. Basically, this feature allows you to navigate through the video using the captions. Not only that, but it allows people who need the captions to read through them first, and get a better idea of how the video is going to play out.
On videos where this feature is available, you'll see a small "Transcript" button underneath the video player. Clicking on that will bring up the transcript, and then you can click on whichever line of text you like to jump around the video. Also very useful when you need something repeated - you no longer have to guess where to move the video slider to.