Unambiguous code means that one codon codes for only one amino acid, e.g., AUG codes for only methionine.
Universal code means that codon and its corresponding amino acid are the same in all organisms, e.g., from bacteria to human, UUU codes for phenylalanine.
Degenerate code means that same amino acids are coded by more than one codon, e.g., UUU and UUC code for phenylalanine.