Apache is open source software. It powers around 46% of websites around the world. Its official name is Apache HTTP. Apache allows website owners to serve and change content on the web. It is one of the oldest and most reliable web servers.
As apache grants an individual to modify the configuration, sometimes it may cause serious security issue if not taken care of properly. It may have slowdown of its server sporadically.
Apache is available to anyone to download at zero cost. The source code can be modified to suit individual needs. It produces frequent updates so that you always have access to the latest features and security patches.