Filter Prefix
A short string added in front of a filter.
The filter prefix is used to automatically append a short text string to the beginning of the filter label name.
For example, suppose my filter group is called "Locations" and I have a filter inside that group with the human-readable name "Botswana" and the label "botswana". If I edit the filter group to have the prefix "geo" then my filter "Botswana" will have its label name changed to "geo__botswana".
Filter prefixes are a helpful way to organize the label names of filters, making them easier to find when typing and for distinguishing filters that have the same name but different meanings (homographs).