All the mobile phones has a dedicated key like power button, camera button, volume up/down button, torch light, etc. For example if you want to capture an image just click the dedicated camera button to capture the images in a short time. These buttons are act as shortcuts for the specific applications.
All the touch mobiles are having dedicated power and volume keys. The volume keys will be helpful to increase or decrease volume when user hearing songs in music player. In some mobiles volume keys are also act as a zoom increase or decrease keys when users launch the camera from the device. The power button can be used to lock your screen or to switch off the mobile. Basic phones also have dedicated keys to put mobiles in silent, turn on/off torch, keypad lock and more.