TALENs

TALENs were a kind of genetic engineering tool. They are restriction enzymes because they can cut specific sequences of DNA. They have a binding domain (strip of bases) and a cleavage domain.
The letters stand for "transcription activator-like effector nucleases". The technique was called "genome editing with engineered nucleases". Together with zinc finger nucleases and CRISPR/Cas9, TALEN was for a while an important tool in genome editing.
TALENs have now been superseded by CRISPR techniques.