There are very few buttons in iPhones, one among them is the home button, round shaped button which you can be found below the touch screen. It is mainly used to return to home screen after using any app. You can opt to use the assistive touch which allows you to add a virtual home button. It is normally active in every iPhone if not just follow these simple steps to activate that

Settings --> General --> Accessibility --> Assistive touch --> ON

and then tap Home .This is moveable anywhere on the screen.

The home button issues are caused either due to software or hardware issues. Hardware would be sending signals but the software is irresponsive this makes the home button irresponsive. When the software is corrupted, overloaded or if the program is crashed the home button stops working. Hardware issues are caused when too much of dust or dirt is being sediment in the home button area or when the home button is being dislocated, the cable connecting the home button and logic board is damaged. iPhone repair center repairs, services and replaces parts of your iPhones.