Absorbent materials are those that can take in other materials — generally liquids. Most materials are absorbent to a certain degree, as absorbency simply requires space within the materials for water to go and cling to. Particularly absorbent items are used in the household to clean up spills.
Paper and Paper Towels
Paper is absorbent due to its property that distributes the liquid evenly. Each part of the paper item will become full of an even amount of water until the cells cannot hold anymore and the piece of paper has reached its absorbency capacity. A paper towel includes more material, so it has a greater ability to pick up spills and dry hands or counters than a normal piece of paper.
Cloth and Towels
Towels and cloth are absorbent because they incorporate absorbent material. Cotton and fibrous materials have a molecular structure that offers a multitude of spaces that attract liquids. Synthetic materials are not as absorbent due to their materials, but many sportswear companies sell "wicking" materials that absorb similarly to paper — by distributing the liquid throughout the cloth.
Hard materials are not as absorbent as cloth or paper, and they vary dramatically in their ability to take in liquids. Wood and natural materials are more absorbent than synthetic materials and metals. (Metals generally do not absorb liquids to any visible extent.) Wood draws in liquids through its vascular interior structure. Most household items have a coating of a special layer of paint or material that either prevents the material from absorbing liquids or prevents rust. Contact with liquid can cause damage that makes the item unusable for its original purpose. Thus, we pick up spills instead of letting them soak into surrounding materials.
Sponges are perhaps the most commonly thought of absorbent material. They incorporate a great deal of open space to allow liquids to move into the material. The thicker the material, the less the sponge is able to absorb it. For example, sponges do not absorb oil as easily as spilled milk. This quality allows the sponge to wipe off other materials to prevent staining, however.