The document discusses gum recession, which is the exposure of the root surface of the tooth due to destruction of the marginal gingiva and junctional epithelium, causing them to re-establish at a more apical position. Key factors that can cause gum recession include bacterial plaque, trauma from improper toothbrushing techniques or materials, iatrogenic factors like overhanging fillings or appliances, and habits like fingernails or foreign objects that cause trauma. Symptoms of recession caused by gingivitis may include bleeding gums, bad breath, and sensitivity to hot or cold.