A frenum is a fold of tissue or muscle connecting the lips cheek or tongue to the jawbone. A frenectomy is the removal of one of these folds of tissue.
Sometimes a frenum can be attached too high on the gums causing either recession or spaces between teeth. The procedure to remove this is a called labial frenectomy and involves the removal of tissue attachment between the two front teeth as the gap between the teeth can again pushed apart by the frenum even after it being initially corrected via a different procedure. A lingual frenectomy removes the fold of tissue under the tongue. Some people have a large frenum that limits tongue movement and can interfere with speech.