A thin client is basically a low-cost PC with no hard drive and usually minimal onboard processing power (CPU and RAM). Because of the limitations of their hardware, you normally can’t install or run applications or save large files on them. They are used to access hosted or server-based virtual desktops and applications.
Businesses prefer them to normal PCs because they cost less and ensure that all of the company’s applications and files remain centralized onto servers, which makes it easier to monitor and manage these IT assets.
The term “thin client” is often used to refer to devices that provide users with access to server-based applications or databases, but that are limited in their ability to install or run applications or store files locally. The term is also frequently used to refer to a particular type of thin computing device, one that resembles a cable modem (though it also comes in “all-in-one” models that are integrated with a monitor, as well as smaller, palm-sized models) and has a CPU, between 500 MB and 4 GB RAM, no hard drive (or a small SSD), a Wi-Fi antenna, Ethernet and USB inputs, DVI and audio outputs, and a low-footprint operating system such as Windows CE. Other types of thin clients include netbooks (including the increasingly-popular Chromebook), nettops, and zero clients, which work without operating systems or firmware.
One reason businesses prefer thin clients is because they prevent users from storing data on their local hard drive. This makes it easier for businesses to secure and back up all of their data, since the data is centralized onto servers. This also ensures that if the physical thin client device is stolen it will not result in the loss of any important data.
Another reason businesses prefer thin clients is because they do not require as much management and maintenance as desktop PCs. For one, the simplistic operating systems and firmware of thin clients do not have to be updated as often as the full-featured OSes and firmware of desktop PCs, and thin clients do not have any locally-installed applications that must be updated. (Zero clients, of course, do not require any updates at all.) The hardware of thin clients is also much more simplistic than that of a desktop PC, so they do not have to be repaired or replaced as often.
Thin clients are also more energy-efficient than desktop PCs: according to this report by the IT department of a European university, thin clients use less than half of the energy of a desktop PC, even when their increased usage of servers and networking equipment is factored in. For most businesses, though, these energy savings, and their associated cost savings, are not really substantial enough to be primary motivating factors in selecting thin clients over desktop PCs—though they may be for very large companies with tens of thousands of desktop workstations, or businesses with a strong interest in environmentalism. Finally, thin clients are significantly smaller than desktop PC towers, which can result in more desk space or legroom for employees, and a more sleek and clutter-free office for everyone.
Larger businesses have the most to benefit from using thin clients instead of PCs. Because they have large numbers of end-user devices, thin clients allow them to reduce their management and maintenance costs and IT-related energy costs by significant amounts.
Thin clients also make sense for organizations—including schools, libraries, and entities with high security requirements (banks, government institutions, research laboratories, etc.)—that want to maintain strict control and oversight over users, and, in particular, prevent users from installing applications and storing data on their local hard drives, without having to deal with imposing and maintaining endpoint security policies and permissions for a large user population.