As a default all videos are hosted on dedicated space provided by AWS.
You also have the option to host your videos in a private channel on YouTube. Doing this gives you additional back-up of the videos and means that you can access them on your own private YouTube account at any time in future.
In order to activate the YouTube hosting you will need to go to your Account section, Project settings and complete the authorisation process there. Note you will need an activated YouTube/Gmail account to do this.
Once activated, if you would like to switch your video to be hosted on YouTube, click on the parallel arrows shown bottom right in the video window:
The arrows will turn magenta and the trademark YouTube arrow in lozenge will signify that you are on YouTube:
You can switch back at any time by clicking the arrows again. You can disconnect the YouTube account at anytime in your Account