This term is often used in the context of Client-Server computer architecture.
Let’s start with some brief definitions
Client ~= a system or computer that accesses services offered by a Server.
Server ~= a system or computer that offers a number of services/resources to Clients.
Service ~= software functionality (e.g. consulting a database, downloading a file) that may be conditioned by certain constraints (e.g. access rights).
Resource ~= a physical or conceptual/virtual/logical object that is part of a computer, and limited in size and availability (space, speed…) example: RAM space, hard disk space, data transmission rate/speed, processor operations per millisecond.
Operating System ~= system/program that interacts directly with the computer hardware and serves as the basis or intermediary between the software/services and the hardware/electronic components that make up the machine/computer. Among its functions: management of files on disks and RAM, communication with input and output devices (screen, keyboard, printer..), user authentication.
Microsoft Windows = a series of operating systems developed by the Microsoft company. (ex Windows 95, Windows 10, Windows Server 2003)
Client-Server Architecture ~= a model of access and sharing of information/resources. In this architecture, data processing is distributed between machines/systems providing services/resources called Servers, and machines/systems requesting services/resources called Clients. These two parties communicate through a hardware/software infrastructure called a computer network, with the particular exception that the same machine hosts both the Client(s) and the Server(s).
From the previous pseudo-definitions, we can conclude that Microsoft Windows Client Operating Systems is the set of operating systems of the Windows series intended to play the role of the client in a Client/Server architecture, it is generally the systems Windows 95, Windows 98, Windows Me, Windows XP, Windows Vista, Windows 7, Windows 8, Windows 8.1 and Windows 10.
No OS can compete with Ms Windows on the desktop market.
First of all, computers are seen by a lot of people as mysterious boxes that never work, where there is always a problem
Source: ventureBeat, 2016
Windows monopolizes the market with its partnerships with education and pre-installation on all computers. The only real advantage of Windows is for gaming
Mac: 9% of the market
The problem with a Mac is that it is very expensive and seen as high-end or even luxury
So we don’t learn at school on Macs but on Windows computers. As I said above, computers are something mysterious so we don’t change our habits. We learned on Windows so we stay on Windows forever. Don’t change the good old habits or you’ll have a disaster. The number of software on Mac is slightly lower than on Windows without it being catastrophic
Windows and Mac draw a line on any form of customization to simplify everything to the maximum. This is not the choice followed by many Linux distributions that allow you to customize at will
Linux: the last percent
No worse than the others on the technical side but much worse on the advertising side. Yes, it’s not easy to advertise something that is free, especially in front of Apple and Microsoft
Apple and Ms are happy that people are still afraid of Linux distributions. It encourages them to stay at home
Another problem with Linux distributions is that you decide everything. The distribution, the desktop, the customization, everything! Except that when you’re not comfortable with computers, you don’t feel capable of that. For those who want to take the plunge, I recommend Linux Mint with the cinammon desktop (by default) to start with, even if you want to change later. My parents (my father recently asked me by SMS where the * key was on the keyboard) manage to use Mint without any problems, I would even say better than with Windows. Forget the rumors that Linux is complicated and reserved for geeks, it is absolutely not true anymore. I never knew Linux when it was still reserved entirely for an elite
No pre-installation. The problem is that most people buy a turnkey computer. The goal? To touch as few things as possible so as not to break everything. So convincing them to install Linux is not going to be an easy task, especially if they don’t see the point of it
There are less software but most of them have an alternative. Once again you will make people scream at trying to change their habits
Since you are talking about computers and not desktops, you should know that the 500 most powerful computers are running Linux:
Note, all operating systems of the TOP500 systems use Linux, TOP500 – Wikipedia
To inspect each type of computer one by one :
Usage share of operating systems – Wikipedia
Most cell phones are running Android which is derived from Linux. Not to forget servers, consoles, connected objects
The only reason why Windows is in the lead is because change scares everyone and Windows has the education market, at least up to higher education (besides, Windows has aged very badly so that computers in high schools, sometimes running XP, are crap and are changed when they could work perfectly with something like Lubuntu)