This developer feature is specifically for users who feel they are proficient in operating Android, for example, they want to try to make Android into a tool that connects to other devices, for example computers / laptops, of course you can. By enabling USB Debugging, all functions on Android can be detected on a computer.
Most people display this developer mode just to enable USB Debugging, either to make an overhaul on a cellphone system, do ROOT with software on a computer, or something else that leads to an Android phone. The best thing when activating USB Debugging, is that cell phones can still be detected even if the cellphone is in a dead state or error. For example bootloop, surely only up to the logo, but if USB Debugging has been activated, it can be directly operated like a remote, for example a factory reset is done, of course it will be very easy.
But there is also a bad thing about activating USB Debugging, which is a virus. Every virus that comes in suddenly can not be seen with direct eyes, and only the antivirus can see it, and block it, but if it has entered and is not detected, of course it will be even more difficult. So it's better not to enable USB Debugging forever, and only when you want to make custom ROM changes, or other operations (changing fonts, systemUI, framework-res) that look a little dangerous.
That way, if the phone has an error, it can still be corrected yourself, unless there is a CWM (recovery) for sure if bootloop, just restore it.
I myself have been helped by activating USB Debugging which at that time my cellphone was not yet ROOT status and suddenly the bootloop was not clear, even though the cellphone was not yet ROOT, it might be a system error. Then I try to plug it into a PC and go into recovery and as a result can be detected properly. Immediately, the factory reset and cellphone returned as new again and no bootloop.
So now you must understand the advantages and disadvantages of activating USB Debugging, and before activating, there is a way to display the developer mode menu, because the USB Debugging feature is on the menu. Here are the procedures, please see below.
How to enable Developer Mode on Android 4.0 and above
1. First of all, please open an Android phone and log in to Settings
2. If it's already in Settings, scroll down and find the menu About Phone.
3. After that on the About Phone page, please scroll down to meet the section Build Number
4. It is known that the Build Number cannot be clicked, but it actually can. Please click 7 times or 10 times, it will appear that the developer mode is active.
5. To go to developer mode, please go back to Settings and scroll down, there will be a new menu called Developer Options.
Very easy right? Let me remind you once again, that this developer mode feature can only be found on Android 4.0 and above, and for underneath the possibility does not exist and USB Debugging-like features must already exist in the Security or Privacy menu.
The Developer Options menu will continue to exist, and to remove it, can do a factory reset. It's better to be careful when setting on the menu, because the feature is specifically for those who have understood the core of the Android structure, so I remind you not to set it carelessly so that the cellphone is in a normal state.
Here I do not want to make users afraid to activate this feature, because I myself have activated it. But just a suggestion, for the USB Debugging section do not always be activated, just at a certain time as I suggested above. If you have anything to ask, please comment.