A drainage hole is an opening designed to allow water to escape from a container or surface. Commonly found in items like flower pots and bathtubs, these holes help prevent water accumulation, which can lead to issues like mold growth or structural damage. In gardening, drainage holes are crucial for maintaining healthy plant roots by ensuring excess water can flow out, preventing root rot. Similarly, in plumbing, drainage holes are essential for directing water away from areas where it could cause flooding or other problems.