The genetic code in humans is about 3 billion letters long. It is made up of just 4 letters A, G, T, C. These letters are called nucleotides and they provide all the information your cells need to make you.
The letters are decoded to make amino acids (the building blocks that make proteins) and there are about 20 amino acids that are made from different combinations of these 4 letters. 3 nucleotides make 1 amino acid.
It’s a bit more complicated than that so watch this video I think you’ll like, it talks about many of the questions you’ve put forward over the last two weeks.