You have likely heard of the exploding popularity of Linux and open-source software. Free server software, operating systems, and applications are rapidly evolving into powerful, mature, and totally customizable software solutions. Few individuals wish to pull their hair out while attempting to master these often arcane beasts, however. 
Fortunately, we can sift through the ever-larger pile of available server software, and find the ones that match a company's specific needs.
The three pieces of server software we most commonly use are Apache, PHP, and MySQL. All three are open source software. Apache is the most widely used web server on the planet, serving up about 60% of the internet's websites. PHP is a scripting language that provides the 'brains' of a web application. MySQL is an extremely speedy and scalable back end database. These three items work in seamless coordination to provide a three-tiered server environment like the one pictured here.
These open-source applications provide cutting-edge performance, increased security, and a price that is impossible to beat. Proprietary software often relies on "security through obscurity", where security holes are never plugged because it is hoped they will never be noticed, whereas these open-source applications have a world-wide base of support that quickly patches security holes and glitches. Performance is comparable to (though usually better than) similar enterprise solutions costing many thousands of dollars.
