Microfilms in the Mormon Library Catalog contain "photographs" of books on birth, marriage, death, baptism. Also censuses, military records, notarial, immigration, books, maps, in short, all kinds of records that may be useful for genealogical research.
There are two types of microfilmed records. One is the Compiled Records: that is, genealogical research carried out by other people, such as: biographies, family histories, genealogies. The second type is the Original Records: that is, those that were created at or near the time of an event, a marriage, a death, a census.
The possibility of having or not having microfilms from a given locality depends on the microfilming contracts that have been made. Some localities, provinces, dioceses, etc. have not allowed the Utah Genealogical Society to microfilm their archives. Others have allowed it but with restrictions for consultation.