Mobile CAPTCHA is a smartphone-friendly version of the CAPTCHA system used on laptops and computers in general. Due to smaller screens, the classical system is impossible to use, so mobile CAPTCHA is usually based on images.
The first time CAPTCHA was used occurred in 2000, the same year it actually was developed. Mobile version was added later in 2006, but only a few years after, it has become well-developed and common. Nowadays it is something that all app developers use.
The purpose of mobile CAPTCHA is to divide people from computers. It can be used as a filter to repel computer programs which should mimic the behavior of actual users. It is also essential for proper web development.
When it comes to marketing, mobile CAPTCHA is mandatory to use. It can divide between computers and actual users, so it can eliminate displaying ads to computers and serve them to humans only.