G A T and C are all bits of DNA (deoxyribonucleic acid)
G stands for Guanine A stands for Adenine C stands for Cytosine and T stands for Thymine, when Guanine is in the DNA it always pairs with Cytosine creating G-C and the same is for Thymine and Adenine, when they are sequenced in such a way it just shows how the DNA is placed.
