Caching means that BS Contact stores downloaded content files on disk. The next time such a file is loaded - either because the user views the same scene again or because the file is part of multiple scenes - then this file can be loaded from disk, which is faster than retreiving it over the net again.
Check for newer versions:
This controls when BS Contact compares the version on disk to the version on the network. The less often this is done, the faster scenes can be loaded. But the more often this is done the lower is the risk to see an outdated file.
Empty cache now:
This deletes all files in BS Contacts cache directory. One can use this to free disk space or to make sure that they see the current version of a scene. It is also possible and harmless to manually delete only parts of the cache directory. To open the cache directory, click on the View button in the Caching tab.
If the Universal Media directory is a sub directory of the cache directory, it is also deleted by this procedure. Whereas if it is not part of the cache directory it is not deleted by BS Contact.
Amount of disk space to use:
Specifies how much disk space BS Contact should use for storing content files. If this limit would be exceeded when a new file should be stored, BS Contact deletes older files first. Older files are also deleted when the Amount of disk space to keep free is reached.
This setting affects the sum of the Cache hard disk directory and the Incremental installation of Universal Media directory.
Amount of disk space to keep free:
Specifies how much disk space should kept free when saving content files locally. If safing a file would mean that there would be less free disk space than the given value, then BS Contact deletes older files first, regardless of the Amount of disk space to use setting.