The Android phones come with a few physical buttons and a few touch-sensitive keys, the latter being usually below the screen. These keys have their own function, and that changes with the way you press them, i.e. normal touch/press and the long press. The standard buttons that are seen below the screen are the Home, Menu, Back, Search, Recent apps etc. and these are not all present in every phone, but the number usually ranges from 3-5 buttons.
The guide below would help you understand what the keys are helpful for, and what would the combinations do, but there is no hard to-be-followed guide hidden below.
Buttons / Keys below the display screen
Back button / key – Takes you to the previous screen where you were there, but won’t take you directly to the home with a single press. When you are typing on the onscreen keyboard and want to close it, hitting the back button would do that.
Menu button / key – The Menu button in the phone opens the options menu of the particular section where you are currently hitting the button. If you are on the home screen and hit the menu button, it would open the options like editing the home screen by adding widgets, shortcuts or changing wallpaper. If you hit the Menu button while inside an application, it would open the options for that app.
Home button / key - Pressing the home button would take you to the home screen, either from anywhere within the app, or from the left or right extra home screens to the center home screen. Pressing and holding the Home button for more than a second opens the list of recently opened applications or the most frequently opened applications and it depends on the phone.
Search button - The search button not just opens the Google search when you are on the home screen, but when you are within any application, it would open the search box to help search within the application. By pressing and holding the Search button, it would open the Google voice search where you talk to make the phone recognize what you said and type that automatically for you.
The four keys that are discussed above, might come as a touch-sensitive one in some, and might be the physical keys in a few phones, though lately it has been mostly the touch-sensitive transparent keys which might not be visible until the display is activated and the light in the background highlights the keys.
Buttons / Keys on the Side Panels
Power button / key - The power button is located usually at top left / right, or on the right side panel and it performs a couple functions, based on the time it is pressed. A normal button press of the Power button would turn off the screen. Long press the power button and it would open the options to switch off the phone, enter the phone into Flight mode, Silent mode and a few other options based on the phone interface.
Volume Up / Down buttons - The volume rocker keys are located on the side panel, and they do what they are named – Changing the volume levels. When the volume down button is pressed for long, it would activate the silent profile. When the phone is ringing, pressing any of the volume keys would silent the phone and this comes handy when you are in a meeting and forgot to keep the profile as “silent” and wouldn’t want to answer to the incoming call.
While you are in an application, music player or the video player, pressing the keys would influence the media volume rather than the Ringer volume.
Camera button - If at all there is any dedicated camera key provided on the right side panel, you could use it to activate the camera and click pictures. When the video recording mode is turned on, the camera button would help in start and end the recording. As a matter of fact, the camera dedicated key has been quite scarce now in Android phones, and most of the phones would need you to do the capture using the shutter icon on the screen itself.
Combination of buttons – Different Functions
The individual buttons function normally with their single job to do, but when combined with any other button, the functioning changes and there are several things that can be usually done by pressing two buttons at the same time. For example, the default Android Phone which has the Android version of 4.0 Ice Cream Sandwich would need the Power Key and the Volume Down key to capture the screenshot, while the button combination would be different based on the phone manufacturer.
The HTC devices with Android 4.0 or later has two options of capturing a screenshot, and all it needs is a key combination. When the Android phones are switched off, it would require you to hold even more than two buttons / keys together when you are doing any developer options like recovering or updating a phone while it is connected to the computer.