Encoding
The work of each cell is done by proteins, so one of the roles of DNA is to build the right proteins for every cell. DNA fills this role by containing three-base sections -- called codons -- that direct the formation of proteins. In a long stretch of DNA, each codon contains the information that directs the assembly of one amino acid onto a protein. Different codons correspond to the assembly of another amino acid onto a protein, so a whole section of DNA with a given sequence of bases will build a specific protein.