A fat client (sometimes called a thick client) is a networked computer with most resources installed locally, rather than distributed over a network as is the case with a thin client. Most PCs (personal computers), for example, are fat clients because they have their own hard driveDVD drives, software applications and so on.
Fat clients are almost unanimously preferred by network users because they are very customizable and the user has more control over what programs are installed and specific system configuration. On the other hand, thin clients are more easily managed, are easier to protect from security risks, and offer lower maintenance and licensing costs.
A system that has some components and software installed but also uses resources distributed over a network is sometimes known as a rich client.