In Plath's poem "Mirror," the speaker of the poem literally is a mirror on the bathroom wall. The mirror says that it has no opinions about what it reflects and that it simply gives images back to the viewer as they really are. It remains alone until someone comes to stand in front of the glass, looking for an image. In the second stanza, the mirror takes on the metaphor of a lake and describes the actions of a woman who comes to the edge everyday looking for answers. She is upset because of some loss in life and the mirror (here the lake) reflects her distress. Over time, the woman grows old and her age is also reflected on the surface.
Figuratively, the poem discusses people's interaction with the truth and that fact that there are times in our lives when we hope to see something in ourselves that is not really there. The woman in the second stanza wants to regain her beauty and youth, but the truth is that she must accept her aging like everyone else.