What is the difference between Google APIs in Android SDK
Since android 5.0, Google added Google APIs. what is that exactly?
A few library jars and corresponding documentation. See the add-ons directory in your Android SDK. From add-ons/addon-google_apis-google-23/manifest.ini:
# details for each librarycom.google.android.maps=maps.jar;API for Google Mapscom.android.future.usb.accessory=usb.jar;API for USB Accessoriescom.google.android.media.effects=effects.jar;Collection of video effectsTypically, you do not need to install Google APIs.
And what is the difference between Google APIs intel atom_64 x86 system image and Google APIs intel atom x86 system image? ... and what version should I use as my main emulator?
One is 64-bit, the other is 32-bit. 64-bit may be slightly faster depending on your machine's architecture. From https://software.intel.com/en-us/android/articles/how-to-develop-and-evaluate-64-bit-android-apps-on-intel-x86-platforms:
Android L with 64-bit technologies for Intel Atom processor-based platforms can help developers to optimize their applications now. Building Android applications for 64-bit is just as easy as building traditional 32-bit Android applications. You can now use the official Android 64-bit emulator to run and debug 64-bit apps. To test the performance of 64-bit x86 Android platforms, we rebuilt several open source projects to 64-bit and had several top ISVs in PRC build 64-bit versions of their apps. The performance benchmarks show 7-8% (or even 20% on one special case) performance gains using 64-bit compared to 32-bit.
Typically, you only need to install Google APIs Intel x86 Atom_64 System Image in order to create an emulator with Google APIs. As mentioned above, you do not need to install the separate Google APIs package.
If you do not use any Google APIs, you could install Intel x86 Atom_64 System Image instead.
Android APIs are part of Google APIs. Google APIs contain Android APIs, Google Map APIs, Google Services APIs, Google Plus APIs and something like that.
Additionally to SilentKnight Answer, Please also refer to this link.
https://developers.google.com/android/reference/packages
https://developers.google.com/android/guides/api-client
Also see Jan Gerlinger answer
What is google API and framework API
According to Jan Gerlinger =
Android is developed by Google, but can also be used without any Google services. So the Android platform SDK can be used for developing Android applications. If you however want to use any Google services in your Android Application, you should use the Google API Java Client library.
And oenpelli answer
According to oenpelli statement =
In the beginning the only Android system images available ran on the ARM instruction set. A system image is used to create different Android Virtual Devices (AVDs) and emulate the different Android devices in common use.
As developer workstations are usually Intel x86 based, the ARM instruction set had to be emulated as well. This resulted in poor performance from the AVDs due mainly to the amount of translation the x86 processor was doing to also emulate the ARM instruction set.
At Android 4.0.3 (API 15) Intel provided their own x86 based Android system image. This could then be used to create AVDs that did not need to do ARM translation. Combined with the Intel Hardware Accelerated Execution Manager (HAXM) the x86 AVMs were up to 10 times faster than the equivalent ARM emulators.
Support for Google specific Android APIs like the Android Google maps API, are not provided with the standard Android system images. They need to be installed separately using the Android SDK Manager. To use these APIs with an x86 system image you need to also install the Google APIs (x86 System Image) for the same API level.