Biographical criticism uses details about an author's personal life to analyse the author's works. It relies on autobiographies, correspondence, and other primary materials about the author and is a form of historical criticism.
The main area in which it is useful is the "roman a clef", the sort of novel which is a thinly disguised account of real people, often including the author, such as Ernest Hemingway's The Sun Also Rises. Critics doing biographical analysis carefully examine incidents in the lives of authors and try to identify events, settings, objects, buildings, people, etc. found in the novels with historical sources.
The difficultly with this sort of criticism, and reason it has somewhat fallen out of favour, is that fictionalized accounts, even when they may have been inspired by actual events and people, often suffer a sea change when they are introduced into novels.
Just as there are many ways to study the human body (one can focus on the circulatory system, the nervous system, the skeletal system, etc.), so too are there many ways to study literature. Each yields different and potentially valuable results. For instance, source study criticism looks at what sources influenced and are alluded to in a particular text. New Criticism, which experienced its heyday from the 1930s-1970s, emphasizes studying only the formal aspects of a literary work: its imagery, symbols, setting, characterizations, themes, etc. It remains the "standard" way we tend to approach a text.
Biographical criticism, on the other hand, studies a literary work in the context of its author's life and, more broadly, his or her historical period. Its key value lies in providing context. Biographical criticism fell into disrepute because of indulging in unsubstantiated claims, such as that Emily Bronte must have had a secret lover because otherwise she could not have invented Heathcliff, or Shakespeare must have been an aristocrat because no commoner could have written such magnificent plays. However, in recent years, biographical criticism has made a comeback as people have increasingly realized that to reach a deeper and more nuanced understanding of a work of art, it is important to know about a writer's life, politics, and preoccupations. As long as biographical criticism enhances, rather than limits, our understanding of a text, it functions as a useful lens through which to study literature.
Biographical approach to criticism means while evaluating a work of art i.e. novel, fiction, drama poetry etc, when one also tends to look into the authors history , his personal life, his physical, psychological conditions of which the poetry is a product. The authors personal life and his times are taken into consideration while evaluating such works.
Example T S Eliot's Wasteland is a result of the social turmoil of his times or his other poems are vague becauseof his emotionally deteriorating conditions.