SmartSVN comes with a couple of pre-installed plugins, based on SmartSVN's Plugin-API. The functionality contributed by plugins may be beneficial to certain users, but is usually either not required for normal usage, or not primarily concerned with SVN.
Plugins are deployed as separate JAR files which are located in the plugins sub-directory in SmartSVN's installation directory. A plugin can be disabled simply by removing the corresponding JAR file from this directory.