ADB (Android Debug Bridge) and Fastboot are two tools allow you to send terminal commands to your phone from your computer via USB.
ADB allows you to send a wide array of terminal commands like basic Linux shell commands but also special developer commands. For example with ADB you can push files to the device.
You can send commands while the phone is turned on and booted, or even when it’s in recovery mode. ADB is often used in conjunction with rooting or modifying your phone.
Fastboot allows you to send commands to the bootloader, which means you can flash/modify things like custom recoveries.
Fastboot isn’t enabled for all phones, so you may have to check your specific device.
You can download these two tools form Android SDK but if you don’t want download the full package (where there are all the developers tools) you can download the Minimal ADB and Fastboot tool created and updated by a user of the famous XDA community, it just contains ADB and Fastboot.
In Windows you must run these two tools from command line, so open a command prompt in the folder where you installed ADB and fastboot, C:Program Files (x86)Minimal ADB and Fastboot by default, you can also modify your path variable (from Windows environment variables -> system variables) to include the folder ADB and fastboot were installed to, so you can run those commands from any command prompt no matter what folder you’re in.
The prerequisite to run these two tools is that the device must be connected to pc (via USB) and working properly.
The drivers references for major smartphones/tablets brands:
Google USB Driver for Nexus.
HTC Sync Manager software HTC that includes drivers for HTC devices
LG support you can search drivers for LG devices
Motorola support you can search drivers for Motorola devices
Samsung support you can search drivers for Samsung devices
Sony support you can search drivers for Sony devices
ASUS support you can search drivers for ASUS devices
Alternatively you can download the universal drivers for any devices.
To make the device and these tools working properly you must first enable Debug USB mode in the device: Settings > About Phone > scroll to the bottom > tap Build number 7 times.
Go back and now access the Developer options menu, check ‘USB debugging’ and click OK on the prompt to enable it.
These tools are used in the following procedures that allow then to install custom Android firmwares (non stock):