A computer server is a specialized computer that serves as the central repository for data and various programs that are shared by users in a network. They are typically more powerful and have more resources than a typical personal computer, and they are designed to handle the increased workload and data storage requirements of a network.

There are several types of servers, including:

1. File servers: These servers store and manage the files that are shared by users in a network.

2. Print servers: These servers manage the printing resources in a network and handle the printing requests of users.

3. Mail servers: These servers manage the email communication in a network, including sending and receiving emails, and storing emails in users' inboxes.

4. Database servers: These servers manage the database resources in a network and handle the requests to access and manipulate data stored in the database.

5. Web servers: These servers host websites and provide the necessary resources for users to access them over the internet.

In addition to these specialized servers, there are also general-purpose servers that can be used for a variety of different tasks.

Computer servers are essential for the operation of a network and play a critical role in the smooth functioning of modern businesses and organizations. They help to centralize data and resources, making it easier for users to access and share information, and they provide a secure platform for the storage and management of sensitive data.