Brash brush for cleaning the end of the nozzle, if it picks up too much plastic (it will).
Keeping the nozzle clean will reduce the potential for getting odd brown spots in some prints when bits fo filament get stuck, turn black/brown and then get left on the part. Doesn't happen too often but some parts do create situations where this can happen (the plastic curls up strongly and then get shit be the nozzle).
This is normally made available as part of the Owner's Kit (which is highly recommended for purchase with your first printer).