Ribose, also known as D-ribose, is an aldopentose - a Monosaccharide containing five Carbon atoms, and including an Aldehyde Functional group. It has Chemical formula C5H10O5.
As a component of the RNA that is used for genetic transcription, ribose is critical to living creatures. It is related to Deoxyribose, which is a component of DNA. It is also a component of ATP, NADH, and several other chemicals that are critical to Metabolism.
Refer to the article on Deoxyribose for more information on both sugars, how they relate to each other, and how they relate to genetic material.