It has default remove, include and weighting filters. You may want to add your own filters to manipulate the list.
Default remove filter removes the hostile and dead targets.
Default include filter includes the pets and players in your party/raid.
Default weight filter sorts the units by their Health percentages and distances if they are out of range.
So, if you want to include non-party members you will need to add an include filter yourself and include them.
If you want to change the order of the units for AoE healing or such, you will need to add a weight filter and sort them yourself