First, let’s clarify the terminology. An is a collection of libraries, documentation, and tools to build software for a specific platform (like Android, iOS, or Windows). The Platform Tools are a subset of the SDK specifically designed to interface with the underlying operating system and hardware.
Without platform tools, developers would have no way to "peek" into a running app to find bugs. They provide the necessary building blocks, debuggers, and libraries that turn a standard computer into a development workstation.
Crucially, Fastboot uses with no flow control beyond the protocol itself. This is why interrupting a fastboot flash can hard-brick a device—the protocol assumes a complete, uninterrupted data stream.
Once detected, the server establishes a cryptographic handshake with adbd .
While ADB operates while the Android operating system is fully booted and running, Fastboot operates on an entirely different level. Fastboot works when the Android OS is completely offline. The Bootloader Connection
When you boot an Android device into fastboot mode (usually Volume Down + Power ), the device loads a minimal USB stack from the bootloader partition. This stack doesn't run Android; it runs a tiny command parser.