IF you refer to the bulit multimedia lessons in PAF 5 you will find a graphical exmaple of what each relationship filter means.
ALso you might not be aware that select and deslecting using the Relationship Filter can be a multistep precedure.
For example you can Start with your cousion and slect Ancestors and it will select only her ancestor, then you go change to an Ancestor and select descendants, then if the is a branch of the family you do not want for some reason higlight that branch either Ancestors and Decendants and select DESELECT.
IT is very powerful, Just takes take. Look at the Lesson on it first