"Apache is a web server. In fact Apache is the world's most popular and dominating web server with over 61% of all Internet web servers running Apache. A far second is Microsoft IIS, with a measly 19% of market share. This is a true testament to Apache's popularity...."
"Apache is not owned by a single commercial entity (like IIS is owned by Microsoft, iPlanet is owned by Sun/Netscape Alliance) but rather, is developed by a loose knit team of voluntary programmers scattered across the globe, collaborating through the Internet. Today, development of Apache is coordinated by a non-profit organization called the Apache Foundation."
"Apache has been written in C, using a dynamic, modular architecture (much like the kernel module architecture) in which pieces of functionality can be inserted into the web server by loading pieces of code known as modules. The pieces of code are built as shared libraries/objects on Unix systems. These pieces of code can also be statically compiled into Apache. This makes Apache highly extensible and configurable."