Both DNA and RNA are made from nucleotides, each containing a five-carbon sugar backbone, a phosphate group, and a nitrogen base.

DNA provides the code for the cell’s activities, while RNA converts that code into proteins to carry out cellular functions.

DNA definition: In cells, DNA(Deoxyribonucleic acid) is the nucleic acid that functions as the original blueprint for the synthesis of proteins.

RNA definition: Ribonucleic acid (RNA) is a nucleic acid which is directly involved in protein synthesis.

Key difference: DNA encodes all genetic information, and is the blueprint from which all biological life is created. And that’s only in the short-term. In the long-term, DNA is a storage device, a biological flash drive that allows the blueprint of life to be passed between generations RNA functions as the reader that decodes this flash drive. This reading process is multi-step and there are specialized RNAs for each of these steps.

There are two differences that distinguish DNA from RNA : (a) RNA contains the sugar ribose, while DNA contains the slightly different sugar deoxyribose (a type of ribose that lacks one oxygen atom), and (b) RNA has the nucleobase uracil while DNA contains thymine.

you can read more from here https://cm.jefferson.edu/learn/dna-and-rna/#:~:text=There%20are%20two%20differences%20that,uracil%20while%20DNA%20contains%20thymine.