Throughout history, poets have tried to explain the nature of consciousness, being, life, ideas and art. Modernist poets such as T.S. Elliot and Ezra Pound, those coming just before the Confessional Poets, tended to write objectively, as academics. They were more interested in the art of poetic creation whereas the Confessional poets openly explored poetry as a means of personal, subjective explication. So, rather than writing a poetic treatise about some abstract universal quality such as love, justice or the material conditions of existence, a Confessional Poet approaches these ideas via their own personal experiences. A Confessional Poet is more subjective in his/her approach to poetry but that does not mean he/she is necessarily less profound in probing life's mysteries. You might even say that a poet like Sexton is just more interested in writing about the experience of love and loss than she is interested about writing about the abstract nature of love and loss.
Sexton started writing relatively late in life, following suicide attempts and institutionalization. Her therapist suggested writing as a form of therapy. This kind of therapy has derived from Sigmund Freud who believed psychoanalysis could be used on patients as a talking cure. Patients would talk about their thoughts, fears and dreams and the psychoanalyst would help them interpret things they talked about. The same idea was used with writing. Thus, here is an example where therapy becomes an art of self expression.
Sexton wrote about different personal themes. Abortion, menstruation and masturbation are some of the more controversial themes she explored. Many of her themes dealt with women's issues. And this, during the 1950's-60's, was a time running up to the Civil Rights Movement; so they were still relatively taboo.
A Confessional Poet writes about his/her personal experiences and indirectly writes philosophically about personal experience itself. Anne Sexton writes a poem about abortion; her personal experience of abortion also contributes to a social understanding of the individual(s) who have gone through such an experience.
Confessional Poetry is often linked to traumatic experiences and psychoanalysis. But it has also been a form to address personal and social issues which had previously not been deemed appropriate topics in literature or just in the general topics of popular culture.