N-terminus
The N-terminal end (also known as the N-terminus, N-terminal domain or amine-terminus) refers to the extremity of a protein or polypeptide terminated by an amino acid with a free amine group (-NH2).
Chemistry
Each amino acid has a carboxyl group and an amine group, and amino acids link to one another to form a chain by a dehydration reaction by joining the amine group of one amino acid to the carboxyl group of the next. Thus polypeptide chains have an end with an unbound carboxyl group, the C-terminus, and an end with an amine group, the N-terminus.
The convention for writing peptide sequences is to put the N-terminal end on the left.
When the protein is "translated" from messenger RNA, it is created from N-terminus end to C-terminus end (right?).