存在 (cún zài) means 'to exist' in a general, often abstract sense — used for problems, relationships, or phenomena. It is more formal and abstract than 在 (zài), which usually indicates a concrete location ('to be at'), and broader than 存 (cún), which focuses on storing or preserving something. 生存 (shēng cún) specifically means 'to survive' (living things), while 现存 (xiàn cún) means 'still existing' (extant).