Sky Q is a box connected to a satellite dish which you connect to your TV. It has the ability to record onto its built in hard drive, anything you want to watch later.
Sky Glass is a TV and is designed to replace your existing TV. It does not record, instead it streams everything via your broadband connection. You must have a broadband connection speed of at least 25Mbps for it to function at all. Instead of recording you create playlists which allow you to watch on demand via various apps.
Sky Stream is a small box you can attach to your existing TV and will stream everything the same way that Sky Glass does, just without you having to buy the Glass TV.
