The Hybrid disc is a combination of a traditional CD/DVD with the new high-definition HD DVD/Blu-ray format, it is the means to enhance the disc's storage capacity and alter between different layers without ejecting and inserting another format disc.
A Blu-ray/DVD hybrid consist of a dual-layer DVD structure and a single layer Blu-ray on top. the total capacity is 33.5 GB (25 GB + 8.5 GB). the disc follows the “Blu-ray Disc, Hybrid Format” specifications provided by the Blu-ray Disc Association. The disc has a blue laser along with two layers like ordinary DVD laser. The Blu-ray and DVD layers are separated by a semi-reflective film that reflects blue light while it allows the red light to pass through the DVD layer underneath.
Note: only certain drives can read both layers of a hybrid disc and also you need hybrid compatible players to play this kind of disc.
With this new added setting, you are allowed to select which layer of the hybrid disc shall be shown by default: Audio CD, DVD, Blu-ray or HD-DVD. It makes your optical drive give the hybrid disc a quick recognize and play the default disc layer easily.