On mobile: iOS and Android

Mobile operating systems

On a mobile device, such as a smartphone or tablet, runs an operating system that enables communication between the software, the hardware and the user. Android and iOS are currently the main mobile operating systems.

Androidis an open source platform and operating system for cell phones, tablet PCs, cameras. It is based on the free and open source operating system Linux. 
Originally Android was developed by the eponymous company Android Inc. Google acquired the company in 2005 and brought the software into the Open Handset Alliance, a partnership initially made up of 34 hardware, software and telecommunications companies. They originally set out to promote the development of open standards for mobile devices. The first cell phone manufacturers with Android were Motorola, HTC, Samsung, LG, Sony Ericsson, and Acer.  

Although Android is an open source system, nevertheless the company Google Inc puts a heavy stamp on the system. Those who use Android will, in most cases, log into the device with a Google/Gmail account. By developing the system in a multi-company community, Android's market share is particularly large. After all, other smartphone developers no longer have to struggle to develop their own system.

For the iPhone, Apple is developing the closed operating system iOS. You can only use this system on an Apple iPhone..  

KaiOS is an operating system for cell phones. It is a fork of B2G OS, which in turn is a successor to Firefox OS. KaiOS is developed for cell phones with relatively modest specifications, also called "smart feature phones" because they are halfway between feature phones and smartphones. In the first quarter of 2018, KaiOS' market share in India was 15%. This makes KaiOS the second most popular mobile operating system in that country after Android.As of June 2018, more than 40 million KaiOS phones had been launched. The development of KaiOS started in 2017. The OS is developed by KaiOS Technologies Inc. based in San Diego, in the U.S. state of California.In March 2018, India's Reliance Retail bought $7 million worth of shares in KaiOS Technologies Inc. equivalent to a 16% stake.[10] Reliance Retail's sister company Jio distributes cell phones using KaiOS. < In June 2018, Google invested $22 million in KaiOS, having previously developed the web apps Assistant, Maps and YouTube for the OS. Some devices have a physical button that allows Assistant to be launched directly. Using the virtual assistant, the phones can be quickly controlled despite their limitations - compared to smartphones. Source: https://nl.wikipedia.org/wiki/KaiOS

Market shares worldwide 

Use of mobile operating systems according to Statcounter (https://gs.statcounter.com/os-market-share/mobile/worldwide)   

Smartphones and data collection

Through its impact on Android and its connection to Google and Gmail accounts, Google has access to a massive amount of user data.