An anticodon is part of a transfer RNA molecule abbreviated tRNA for short. The anticodon consists of 3 nucleotides that match the base pairs of a specific codon on messenger RNA. The other end of a tRNA molecule carries one of the 20 amino acids used to build proteins.
Molecules of tRNA act as tow trucks to transport amino acids to the ribosome where protein synthesis occurs. Ribosomes are large complexes of ribosomal RNA and proteins. They match up codons on mRNA with anticodons on tRNA then link the appropriate amino acids into a growing chain called a polypeptide or protein. When the ribosome hits certain codons called stop codons, there's no corresponding tRNA with which to match them. At this juncture, the ribosomal subunits separate and release the finished protein.