Where exactly is DNA found in the body? What are the biggest difference between DNA and RNA?

DNA is found in the nucleus of every single cell of the human body. It may be expressed differently depending on the cell, but the same DNA is found in every cell of your body. The only exception to this rule is that sex cells, or gametes, are different. These are the cells involved in reproduction.

RNA contains a ribose sugar with an oxygen atom, whereas DNA contains a ribose sugar without oxygen atoms, hence it is called deoxyribose nucleic acid. DNA is double stranded whereas RNA is single stranded. The nucleic bases also differ: in RNA we have uracil instead of thymine.

Functionally, DNA is the blueprint for genetic information and is stored in the nucleus whereas RNA plays several roles and operates outside of the nucleus. DNA provides the template for cell division by both mitosis and meiosis, as well as for protein synthesis to occur in which RNA plays a major role. RNA also transmits information from DNA to ribosomes in order to make proteins.

You can read more about the differences between DNA and RNA in this Socratic answer and this one.