Extending your forum
While developing SMF, the developers try to balance the software so that it does not contain features most administrators would not want (which would hinder performance), but still stay at a level where it is up to date with its competitors and the internet trends for its time. Unfortunately, it is impossible to always meet the needs of everyone, and certain features and functionality may not meet everyone's needs because of the wide range of administrators that use SMF. Fortunately however, SMF can be extended from its core package so that it can ultimately exceed most administrative needs. This is in thanks to mods (modifications), which are sometimes referred to as hacks, especially in some other web software packages.
So what are mods?
With mods, you can add additional features to your forum, modify the functionality of existing features to meet your needs, install avatars and language packs, and really do essentially anything that is within the constraint that the package manager will allow you to do to alter your forum.
Extending your forum the easy way
If you are new to SMF but have used another forum software, you may have had the unfortunate experience of having to manually make changes to the codebase by looking at a file and doing a continuous find and replace of many lines of code. SMF relieves this tiresome burden, with its Package manager, which will automatically install and uninstall mods for you with the click of a button.
Finding mods and installing them
Most mods released for SMF can be found on the SMF Customization Site. For information on installing mods on your forum, please see the documentation for the Package Manager section of your admin panel.