1 (not used in the continuous tenses 不用于进行时) to be real; to be found in the real world; to live 存在;生存:
Dreams only exist in our imagination.梦境只存在于我们的想象中。Fish cannot exist out of water.鱼离开水就活不成。
2 exist (on sth) to manage to live 继续生存:
I don't know how she exists on the wage she earns.我不知道她怎么靠她挣的工资生活。