Five Buttons of iPhone

The iPhone has a minimal hardware user interface, featuring five buttons.

 Eventually only the physical menu button is situated directly below the display, and is called the "Home button" because it closes the active applications  and navigates to the home screen of the interface.

 The home button is denoted not by a house, as on many other similar devices, but a rounded square, reminiscent of the shape of icons on the home screen.

A  several function sleep/wake button is located on the top of the phone.
 It serves as the unit's power button, and also controls phone calls. 
When a call is received, pressing the sleep/wake button once silences the ringtone, and when pressed twice transfers the call to voice-mail. 

Situated on the left spine are the volume adjustment controls button. 
The iPhone 4 has two separate circular buttons to increase and decrease the volume; all earlier models house two switches under a single plastic panel, known as a rocker switch, which could reasonably be counted as either one or two buttons.

Directly above the volume controls is a ring/silent switch that when engaged mutes telephone ringing, alert sounds from new & sent emails, text messages, and other push notifications, camera shutter sounds, Voice Memo sound effects, phone lock/unlock sounds, keyboard clicks, and spoken auto correction speakers indeed.
 This switch does not mute alarm sounds from the Clock application, and in some countries or regions it will not mute the camera shutter or Voice Memo sound effects.