The SME Server is characterized by its tight focus on providing network server functions. For the end-user, the SME Server provides simple, extensible web-based management. For developers, the SME Server provides clean, consistent, extensible interfaces to allow features to be added and modified.
Some Linux distributions are aimed at desktop users, general purpose server applications, or "enterprise" server applications. The SME Server is different in that it is targeted towards providing network server functionality for small to medium enterprises. Because of this, the SME Server is much smaller than many other Linux distributions, as software packages which are not needed for this purpose (for example, the X window system) are not included in the distribution.
The SME Server is also simple for a non-technical person to manage. For an end-user administering the server, choices are kept to a minimum. If a decision is very likely to be the same for all small businesses, the answer is assumed and the end user is not required to make a choice. When decisions are required, they are phrased in terms independent of the underlying technology, so that end-users are not required to be intimately familiar with Linux or Linux applications.
For developers, the simplicity is in the architecture of the SME Server system. Features are layered in such a way that additional features can be added without affecting the current services, and often without requiring modifications to the user interface.