Lighttpd (pronounced "Lighty") is an open-source web server known for its lightweight, fast, and efficient nature. It's designed to provide a slim and powerful web server that remains stable and reliable even under high loads.

Some key features of Lighttpd include:

1. Lightweight: Lighttpd is known for its low resource usage compared to other web servers like Apache. This makes it particularly well-suited for environments with limited resources or for use on low-powered devices.

2. High speed: Lighttpd is engineered to serve web content quickly and efficiently. Its architecture and optimized implementation allow it to perform well even under heavy loads.

3. Flexibility: Lighttpd supports various features and modules, including support for FastCGI, SCGI, CGI, proxying, SSL, and more. This versatility makes it adaptable to various requirements.

4. Security: Lighttpd prioritizes security and offers features such as SSL/TLS support, URL and access control rules, as well as protection against known security vulnerabilities.

5. Simple configuration: Lighttpd's configuration is done through a simple and clear configuration file. This makes it easy to configure and customize the web server, even for users with little experience.

Due to its characteristics, Lighttpd is often used for applications that require high performance, scalability, and efficiency, such as high-traffic websites, content delivery networks (CDNs), streaming media servers, and more.