[Inkscape-user] Filters Effects

Please help me understand Filer effects! I'm trying to play with the filters but I must be missing something, they have explanations of what they do in the UI but when I try them most of them only turn the shape into a black / white/ transparent rectangle that looks like a bug. The only ones I got to work are blur and color matrix. Are they supposed to work? do they only work for certain type of object?

Also, I don't understand something in the UI. In the filters dialog there's this complicated looking effect/connections table which I can't seem to do anything with.

Is there an explanation somewhere on how to work with all this?