A frenum is the fibrous tissue that connects the upper and lower lip to your gums. Also, another is under the tongue where the tongue is attached to the floor of your mouth. When these tissues are too tight, it can interfere with orthodontic treatment, gum health, or speech delays. Tight lingual frenulum can also be referred to as a tongue tie. The process of clipping this tissue to help resolve these issues is called a frenectomy.