DNA is held in the nucleus/control center of the cell. It's protected here because it holds valuable information about which protiens to make. Each part of the DNA inside you codes for different cells to be produced.
The shape of DNA is a double helix, which is basically a twisted up ladder. The rungs of the ladder are two different nitrogen bases hooked together. There are four nitrogen bases total; Guanine, Citozine, Thymine, and Adenine. Guanine and Citozine always link together, and Thymine and Adenine always link together. These pairings are called 'nitrogen pairs'. The order of these pairs determines whether you have brown hair or blonde, if your tall or short, and if your a human or a frog! The possibilities for these orders are limitless.
The outside of the ladder is made up of deoxyribose sugar and phosphate. They are held together by strong covalent bonds, which never break. The sugar/phosphate outside is important because it holds everything together
DNA doesn't just hang out in the nucleus, it's constantly splitting and replicating itsself. Helicase splits the DNA straight down the middle, breaking the weak hydrogen bond that links the two nucleotides(nitrogen bases) together. RNA then carries the DNA to an enzyme called polymerase, which creates the opposite pairs of the single row of ntrogen bases on each little "half ladder'. Finally, ligase stitches everything back together and the same exact strand of DNA is produced.
RNA is structurally similar to DNA, but they have very different roles. Think of DNA as an origional document. It stays locked up safe in the nucleus and sends out the RNA copies to tell ribosomes which protiens to make. RNA is single stranded, which means it is not a double helix. It also has a different outer wall, which has ribose sugar instead of dioxyribose sugar. RNA is very important because without it, the important information would never be spread around the cell.