DNA at its simplest is made out of molecules. Molecules are just clumps of atoms. For example a water molecule is made up out of one Oxygen atom and two Hydrogen atoms. DNA is a more complicated version of that example. DNA as a molecule is actually a collection of molecules. Four of them being Adenine, Thymine, Guanine and Cytosine. The order in which these molecules are bonded to each other in the DNA molecule strand can be read as a genetic code, A T G or C.
To go into a bit more depth without [hopefully] sacrificing any readability.
A chromosome is a single strand of DNA, a single molecule.
DNA itself is a polymer [literally: poly-mer, many-parts] made up of monomers [mono-mer, one-part] called bases or nucleotides which include A, T, G and C for DNA. Any organism made up of DNA will have its entire structure encoded within those four base pairs. Organisms which use DNA include anything you’ll actively interact with, though at the smaller scale things do change a fair bit.
The chain itself is made up of alternate phosphate and ribose links, with the base portion being attached to only the ribose portion.
There are a number of other types of organic polymers related to DNA which are used in your body every day. RNA is the most similar, it merely has a U instead of a T nucleotide and is single stranded.
There are also proteins which are directly encoded from DNA/RNA by way of Amino Acids. Amino Acids are a macro molecule, each of which is associated with at least one three base combination. So, when you have a strand of RNA being ‘made into’ a protein, you’ll have a series of Amino Acids combine in a similar manner to the video here to create a single Protein.
Proteins are the real driving force of the body, they’re the macromolecules which actually transcribe DNA. Certain types of Proteins are known as Enzymes. Each ‘bit’ attached to DNA in this video is a protein. Proteins work by doing specific things enabled by their physical structure. The exact structure is dictated by the electroweak force and thus, quantum physics!
There are other base pairs which have been created in the lab, it’s unknown why we havn’t seen these in nature much like a lot of abiogenisis [natural process by which life arises]. There is the study of un-natural life called Exobiology [exo- meaning ‘outside of-‘], which is a particularly awesome field, imo!