Different Types of CMS

There are a lot of different Content Management Systems available, and beside the main common feature of offering the division between layout and content, the modes of operation can be very different.

Flatfile-CMS

On a flatfile-based CMS, the content is (usually) saved in clear text files. Depending on the concept, layout elements can be saved in separate text files as well, dividing layout and content, and having the CMS put those two together on accessing the page (or any other defined action).

Database-managed CMS

With a database-managed CMS, all data is saved in a database and will be requested from there. Using such a system therefore requires a database (including the rights to modify it).

From a technical point of view, using a database has the advantage of a better scaling system on really huge amounts of data - provided that the database is properly accessible. On the other hand, a flatfile-based CMS can be much faster with a moderate amount of data, just because the database communication is not needed. This can be especially important in a shared-host environment (one server, multiple domains hosted), as server load and reduction thereof directly influences the website speed.

Portal systems

Portal systems still are very popular, and there are a large number of different systems (especially in the open source sector). The main advantage of those portals is often their main disadvantage: Using such a system, you can easily (and in a short time) build a complete portal that can be changed in look and feel using "themes" and "skins" (prepared layouts).

On the other hand, those "themes" and "skins" make portal systems quite inflexible when it comes to own enhancements, modifications and changes. Especially regarding the page design, a user has only very limited options. Additionally, nearly all portal systems need a database, and most are a bit on the slow side. Those who just want to set up a portal quickly might be well advised to use such a portal system, but if you have specific ideas or need special functionality, you might find portal systems lacking some flexibility.

source: http://docs.phpcms.de