Every sink has a trap. The purpose of this trap is to create a water barrier to keep the sewer gases from entering your home. Over time, this pipe can get clogged from soap scum, hair and other debris. The best way to clear that blockage to is remove and clean the trap.
First, place a bucket under the trap to collect the water. Loosen the slip nuts on each end. Gently remove the trap and dump out the water. Clean out any debris that might remain. Simply reinstall it by putting it back into place and tightening the nuts. Make sure the fittings are properly aligned and the O-rings are in place. Do not overtighten the nuts. Test it by running the water for a few minutes to ensure there are no leaks.
Clogged sink drains are pretty common, but clearing them out is a simple task. And you can do it!