The answer to a clogged drain is that it is usually caused by a buildup of hair, soap scum, or other debris in the drain pipe. Symptoms include slow draining water, standing water, and sometimes unpleasant odors. The most common solutions are using a drain snake or plunger to remove the clog, or using a chemical drain cleaner to dissolve the blockage.
If the clog is deep in the pipes or difficult to clear, it's best to call a professional plumber. They have specialized tools and expertise to properly diagnose and fix the issue without causing further damage to your plumbing system.