When the Android SDK was first made available to the world, Google used QEMU as the basis for their Android emulator. They copied the source code to a custom repository in the Android Open Source Project (AOSP) and made a number of invasive modifications to QEMU. Specifically, they added emulation of a specific board called goldfish for the purposes of emulating an Android phone.
Every build of Android targets a specific hardware platform, and the emulated goldfish platform is no different. A number of specific emulator features are enabled in both the Android kernel and Android userspace environment when run in an emulated environment. These features allow a smooth and complete user experience resembling using a real Android device, on laptop and desktop workstations.