DNA, deoxyribonucleic acid abbreviated, is a lot like strands of sequences. DNA consists of hydrogen, nitrogen, oxygen, phosporous, and other things. It has these things called nucleotide bases.
Nucleotide bases bond with each other, and this is important to the DNA's structure and to an important role it plays in life. The nucleotide bases are adenine, thymine, cytosine, guanine. One important thing to remember when studying DNA is that adenine can only bond with thymine (and vice versa), and cytosine can only bond with guanine (and vice versa).
You might see something like AATTGCCCGG. Well, it's a lot less complex than it seems. Those letters just stand for nucleotide bases. A = adenine, T = thymine, C = cytosine, G = guanine. You might get asked one day what the corresponding sequence of a DNA sequence would be. Well, we know what bonds with what, so it would be TTAACGGGCC ( for AATTGCCCGG).
DNA can code for the production of proteins in a process called transcription. In this process, DNA exposes a relevant portion of itself, and in this process, individual nucleotides of RNA bond with the exposed portion of DNA, which forms a strand of RNA. Now, we won't even go into the functions of RNA, but I will tell you that it's called ribonucleic acid, and it also has four nucleotide bases (four different kinds NOT just four total on every strand). They're adenine, uracil, cytosine, and guanine. Yep, DNA and RNA have three nucleotide bases in common with each other. They also have different sugars. DNA has deoxyribose, and RNA has ribose. The uracil of RNA just takes the place of thymine, and functions exactly like thymine during transcription. So, uracil bonds with adenine (and vice versa). I mentioned this because coding for the production of proteins is a very important thing and DNA is responsible for it.