Settings

• The Apple Watch uses the S1 system-on-chip.
• It uses a linear actuator called the "Taptic Engine", this provides haptic feedback when an alert or a notification is received.
• Built-in heart rate sensor (uses both infrared and visible-light LEDs and photodiodes). This is especially designed for excercising purposes, and can keep track of your health in general. 
• All version have 8 GB of storage (2 GB of music and 75 MB of photos). It doesn't matter which one you buy, they are all of the same storage. 
• Watch is paired with an iPhone, therefore all the music on the iPhone is on the Apple watch. You won't have to go through the hassle of uploading them again on your apple watch.