The sequence of nucleotides in DNA that determines the sequence of amino acids in a polypeptide via an mRNA intermediate is known as genetic code.
The genetic code is a triplet code. Three consecutive nucleotides in mRNA constitute a codon which codes for a particular amino acid.
There are 64 codons where each codon is a triplet and 61 of them code for specific amino acids but three do not code for any amino acid and hence are called stop codons (UAA, UGA, UAG).
One codon codes for one amino acid due to which it is said to be unambiguous/specific. E.g., AUU always codes for isoleucine.
The genetic code is degenerate because one amino acid can be coded by different codons.
E.g., AUU, AUC and AUA, all code for isoleucine.
UUU and UUC codes for the same amino acid phenylalanine.