curl is a command-line tool used to transfer data to or from a server. It supports various protocols, including HTTP, HTTPS, FTP, and more. Users can easily download files or send data using simple commands, making it a popular choice for developers and system administrators. In addition to its basic functionality, curl offers many options for customization. Users can specify headers, manage cookies, and handle authentication, allowing for more complex interactions with web services. Its versatility and ease of use make curl an essential tool for anyone working with web technologies.