Codons on mRNA pair with anti-codons on TRNA
Genetic code is redundant ( 64 different codons for 20 amino acids)
Redundancy protects from mutation (in principle)
Exceptions to the genetic code: Mitochondria and protists have different start and stop codon identities,
Lastly there are the two nonstandard amino acids which are used via transnational recoding and are not a part of the genetic code itself.