A mattress topper is a thick, cushioned layer designed to be placed on top of a mattress to improve comfort, support, and longevity. It can help adjust the firmness level, relieve pressure points, and enhance sleep quality. Available in materials like memory foam for contouring support, latex for breathability and durability, gel-infused foam for cooling, and down or fiberfill for plush softness, mattress toppers cater to different sleep preferences. They are also a cost-effective way to refresh an old mattress or customize the feel of a new one.