DNA is a polymer that contains deoxyribose and a phosphate backbone. It contains these 4 nitrogenous bases: Adenine, Guanine, Cytosine and Thymine.
RNA on the other hand is a polymer that contains ribose and phosphate backbone. It contains 4 nitrogenous bases of: Adenine, Guanine, Cytosine and Uracil.
Hope that helps a bit.