A hagiography is a biography of a saint. The term is also used to describe the study of saints, although some people prefer to describe the study of saints as hagiology. Hagiographies have an ancient and esteemed history in Christian culture, and they are also present in several other religious traditions, especially Buddhism and Islam.
The art of hagiography arose early in the days of the Christian church, when it was used primarily as a propaganda tool. The idea was that by disseminating information about the lives of the saints, Christians could conceivably win converts. Hagiographies were far from dull accounts of history; they included inspirational stories and set up legends and myths about the people in them. Many hagiographies also included ghoulish descriptions of martyrdom, undoubtedly to appeal to people with more base sentiments.
In addition to being used to spread Christianity, hagiographies were also utilized as a tool to sanctify people. Many notable ecclesiastical figures and other church authorities commissioned hagiographies of themselves in the hopes that they would later be venerated as saints, and this was sometimes successful. In all cases, a hagiography typically stressed the subject's bravery, intrepid spirit, and Christian faith.
The heyday of the hagiography occurred in the medieval era, when numerous hagiographies were produced, both individually and in collections. During this era, many people created calendars of the saints, and those who could read were able to learn about a different saint each day; a medieval version of the page a day calendar, as it were. Many of these calendars have since been canonized, and a calendar of saints days exists today in both the Catholic and Orthodox churches.
Although the hagiography is treated as a bit old fashioned in the modern era, it is still possible to find well-researched scholarly works on the lives of the saints, along with more traditional hagiographies. Some of these materials are quite interesting, documenting the lives and works of early moves and shakers in the Christian church, as well as the activities of more modern saints.
Because a hagiography was typically designed to present its subject in the best possible light, you sometimes hear “hagiography” used as a slang term to describe a secular biography. When used in this sense, a hagiography is a fawning, uncritical, and often poorly researched biography which paints a very adulating picture of its subject, rather than an accurate discussion of someone's life and works.