DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid) are those molecules involved in the storage of our genetic information (DNA), but also in the production of amino acids for proteins (RNA).
Both molecules have a particular structure comformed by nucleotides, a pentose, and a nitrogenous base (Adenine, Thymine, Cytosine, Guanine for both, and Uracile for RNA, which replace Thymine when it replicates the information of DNA in mRNA).
Another difference between these molecules relies on a particular extra oxygen atom they have in a particular C position on the pentose (carbon ring), that in RNA is present, while in DNA not.
One of the main differences in these molecules is that DNA is only found in superior organisms, like animals, plants, or macroscopic fungi, while RNA is only found in other organisms like bacteria or virus, although RNA develops the function of replication in superior organisms.
Also, we could say that the molecule of DNA is a double-stranded molecule (conformed by two complementary strands from DNA), while RNA is linear in most cases, and also circular.
DNA differs too from RNA in that also DNA is packaged in our chromosomes with some proteins called histones, which compacts this molecule.