https://phys.org/news/2018-06-microbe-universal-dna.html

All organisms receive genetic information from their parents which tell the cells how to make proteins—the molecules that do the chemistry in our bodies. This genetic information comprises DNA molecules made up of a sequence of four chemical bases represented by the letters A, T, C and G; the genetic code dictates to the cell which sequence of amino acids to join together to form each protein given the underlying sequence in the DNA.

In a similar way that "dot dot dot" in morse code translates as S, so too the genetic code is read in blocks of three bases (codons) to translate to one amino acid.