Network Navigator - Filter Field

Hi,

Can anyone please tell me how the Filter field is used within the Network Navigator field?

I've tried searching the web and working it out for myself, but to no avail. I was hoping that it might be linked to the search box within the visualisation (i.e. to highlight any nodes/targets matching a specified string) but this doesn't seem to be the case, but it's left me feeling curious as to what it's actually used for!

Thanks,

Pete