Some sites cache to memory, while others may cache to other mediums, such as flat files. On the backend, there's usually some sort of database driven CMS for maintaining content and publishing rules.
Thanks for the info. I've read about some open source content management systems. Anyone here familiar with, and which are considered industry standard? I'm interested for general knowledge (and maybe something to play around with), not a commercial project.
In the Java domain, OpenCms is the standard bearer, with Magnolia being a (somewhat distant) runner-up. Some non-Java CMS'es are more popular, though, e.g. Typo3.