Codon tables describe how the triplet codon of RNA (or DNA) is read by specific tRNAs to map to a particular amino acid. Many organisms use the Standard Codon Table, shown below.
Comprehensive information about codon usage in different organisms can be found at the NCBI Taxonomy site
Standard Codon table
1The codon ATG both codes for methionine and serves as an initiation site: the first ATG in an mRNA's coding region is where translation into protein begins.
2UGA can also code for selenomethionine: the twenty-first amino acid, discovered in 1986.
3UAG can also code for pyrrolysine: the twenty-second amino acid, discovered in 2002.