What can I deduct as "Outside Services"? What are the rules on what qualifies as Outside Services? I hire out small tasks to independents, do they qualify as a deduction?

I understand that if I pay less than $600 per month to what I understand are people providing outside services, it's OK to not have a 1099. But I can't find a good definition of the outside services tax deduction anywhere. Just need a list of rules to go by.