The Raspberry Pi is a series of small single-board computers developed in the United Kingdom by the Raspberry Pi Foundation to promote the teaching of basic computer science in schools and in developing countries. The original model became far more popular than anticipated, selling outside its target market for uses such as robotics. It does not include peripherals (such as keyboards and mice) and cases.
According to the Raspberry Pi Foundation, more than 5 million Raspberry Pis were sold by February 2015, making it the best-selling British computer. By November 2016 they had sold 11 million units, and 12.5m by March 2017, making it the third best-selling "general purpose computer". In July 2017, sales reached nearly 15 million. In March 2018, sales reached 19 million. Most Pis are made in a Sony factory in Pencoed, Wales; some are also made in China and Japan.
Raspberry Pi Trading's CEO Eben Upton said in December 2019, that more than thirty million boards had been sold.
The first generation (Raspberry Pi 1 Model B) was released in February 2012, followed by the simpler and cheaper Model A. In 2014, the Foundation released a board with an improved design, Raspberry Pi 1 Model B+. These boards are approximately credit-card sized and represent the standard mainline form-factor. Improved A+ and B+ models were released a year later. The Raspberry Pi 2, which added more RAM, was released in February 2015.
Also in November 2015, the Raspberry Pi Zero was released, this was a smaller physical size than the original Raspberry Pi and had a reduced number of input/output sockets, but was considerably cheaper and proved very popular for use in embedded projects.
February 2016 saw the Raspberry Pi 3 Model B released, which was again credit-card sized, but had a faster processor and both Bluetooth and WiFi on board. Two years later the Raspberry Pi 3 Model B+ was launched, this was again faster than its predecessor and had dual band WiFi and a faster ethernet connection.
The Raspberry Pi 4 Model B was released in June 2019 with a choice of memory configurations, namely 1GB, 2GB, or 4GB of the stuff, the ethernet was now a real gigabit connection, the processor was newer and faster than any of the previous models, it had USB2 and USB3 connections, two micro HDMI sockets for dual monitor support, and the power connector was changed from the micro USB used by the earlier models to a USB-C connector that could supply the extra power needed by the more powerful chips. In May 2020 the Raspberry Pi 4 Model B had an 8GB version added to the lineup and the 1GB version was discontinued.
And this web page has just been delivered to your screen from one of four Raspberry Pi in a cluster, running web server software. (The multiple Raspberry Pi cluster gives some measure of redundancy. If one unit fails for any reason, the rest carry on regardless.) They cost less than 2 pence a day to run and are absolutely silent. I have another on my desk that I use for day to day computing, emails, web-browsing etc. Another Raspberry Pi records the footage from my CCTV security cameras, and two others are just spares. That is until I can find a use for one or both of them.
The reason I have two spares is because one used to monitor the battery voltage and charging current on my solar farm, but I replaced it with a smaller cheaper unit because using a Raspberry Pi was just a waste of a good Raspberry Pi. The last one was used as a fileserver on my network, but it outlived the hard disk that the files were on and is now sat on a shelf awaiting its next job.
TL;DR - Conclusion.
I do have a normal PC, but I can't remember the last time I switched it on. It sounds like a vacuum cleaner when the fans start spinning and all the little lights start flickering, and it doesn't do anything that a Raspberry Pi won't do in total silence, except for graphic intensive games that I'm not all that bothered about playing anyway.