Network services refer to the various functions and capabilities that are provided by a computer network to enable communication, sharing of resources, and efficient management of data. These services are typically implemented using specialized software and hardware components. Among the given options, all of them - file service, print service, and database service - are examples of network services.

1. File Service:
A file service is a network service that allows users to access and share files stored on a centralized server or distributed across multiple networked devices. It provides a convenient way to organize, store, retrieve, and manage files within a network. With file services, users can access files from any connected device and collaborate with others by sharing files and folders.

2. Print Service:
A print service enables users to send print jobs from their devices to network-connected printers. It allows multiple users to share a single printer, eliminating the need for individual printers at each workstation. Print services also provide options for managing print queues, controlling access to printers, and monitoring print jobs.

3. Database Service:
A database service provides a centralized platform for storing, managing, and retrieving structured data within a network. It allows multiple users to access and manipulate data simultaneously, ensuring data integrity and security. Database services are commonly used in applications that require efficient data storage, retrieval, and processing, such as enterprise resource planning (ERP) systems, customer relationship management (CRM) systems, and online transaction processing (OLTP) systems.

By offering these network services, organizations can enhance productivity, improve collaboration, and streamline data management. These services facilitate the efficient sharing of resources, such as files and printers, across the network, enabling users to access and utilize these resources from any location within the network.

In conclusion, all of the given options - file service, print service, and database service - are examples of network services. These services play a crucial role in enabling communication, resource sharing, and data management within a networked environment.