Android Operating System
Android OS is a Linux-based platform for mobile. Android was released under the Apache v2 open source license.
Android was developed by Google and the Open Handset Alliance (OHA), a coalition of hardware, software and telecommunications companies.
More than 30 companies were involved in OHA, including Qualcomm, Broadcom, HTX, Intel, Samsung, Motorola, Sprint, Texas instruments and Japanese wireless carriers KDDI and NTT DoCoMo.
Android began its life as a Polo Alto-based startup company, founded in 2003. That company was subsequently acquired by Google in 2005.
Android Open Source Project
Android is a widely-adopted open-source project. Google actively develops the Android platform but gives a portion of it for free to hardware manufacturers and phone carriers who want to use Android on their devices.
Google only charges manufacturers if they also install the Google apps portion of the OS. Many (but not all) major devices that use Android also opt for the Google apps portion of the service.
One notable exception is Amazon. Although Kindle Fire tablets use Android, they do not use the Google portions, and Amazon maintains a separate Android app store
Google Play (Android Market)
Anyone can download the SDK (software development kit) and write applications for Android phones and start developing for the Google Play store.
Developers who sell apps on Google Play market are charged about 30% of their sales price in fees that go to maintain the Google Play market.
(A fee model is pretty typical for app distribution markets). Some devices do not include support for Google Play and may use an alternative market. Kindles use Amazon’s own app market, which means Amazon makes the money off any app sales.
Because Google developed Android, it comes with a lot of Google app services installed right out of the box.
Gmail, Google Calendar, Google Maps, and Google Now are all pre-installed on most Android phones. However, because Android can be modified, carriers can choose to change this. Verizon Wireless, for instance, has modified some Android phones to use Bing as the default search engine.