Suction is the flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area. Suction is popularly thought of as an attractive effect, which is incorrect since vacuums do not innately attract matter. Dust being "sucked" into a vacuum cleaner is actually being pushed in by the higher pressure air on the outside of the cleaner.
The higher pressure of the surrounding fluid can push matter into a vacuum but a vacuum cannot attract matter.
Humans can create a sucking effect with the use of the lips, as in the case of drinking through a straw.