any fan that blows on your plants helpA desktop fan is typically static and does not turn (oscillate); comes in various sizes with or without a Clip attachment.
Oscillating fans have the option to distribute the air flow side to side. i.e. It turns.
Oscillating fans encourage stem growth/strength; which in turn helps hold up those massive nugs we all love.
A fan that is non-oscillating and blows directly on the plant is not a good thing; for various reasons.. Air Flow/unintentional training (The plant starting to lean over due to constant air flow)...etc..etc..
Hope that helped!