A short dictionary of detection terms:
Caper -- A story built around the detailed planning and execution of an elaborate crime. More popular in movies than books, but Donald Westlake has written some corkers.
Cozy -- A "traditional" mystery whose best-known practitioner is Agatha Christie. Common elements include: a domestic setting such as a country house or quiet neighborhood; a limited roster of suspects, all part of the victim's social circle; little or no description of violence or sex; a mildly romantic subplot; and an amateur sleuth or eccentric professional.
Fem-jep -- Short for "female in jeopardy," a sub-genre most often seen in movies of the week, wherein a lovely young women is placed in a perilous situation, e.g. stalked by a crazed killer, and the rest of the plot is devoted to her rescue by a white knight. Also known as WIP, or woman in peril.
Golden Age (of mysteries) -- The period between the World Wars, when detective novels became extremely popular and the "conventions" of the genre were established. Many Golden Age writers are still in print, including Christie, Dorothy L. Sayers, Marjorie Allingham, Ngaio Marsh.
Had-I-but-known (HIBK) -- An early form of gothic or romantic suspense, in which the eponymous phase is used by the first-person heroine addressing her readers.
Hard-boiled -- Another traditional sub-genre, originally found in the "pulp" detective magazines but reaching literary excellence in the works of Raymond Chandler and Dashiell Hammett. Features a lone-wolf private detective, cynical yet quixotic; the mean streets of the inner city; characters from both the professional criminal class and the criminally rich; and liberal additions of violent action and disassociated sex.
Inverted mystery -- A story in which the reader knows whodunit, but the suspense arises from watching the detective figure it out. This is a popular form for mystery TV-movies; the best-known example is the Columbo series.
Macguffin -- An object which is pursued by the characters in a story purely for the purposes of propelling the plot, without having any intrinsic relationship to the solution of whatever mystery arises in the course of the pursuit. Best-known example: the Maltese Falcon. The term originated with Alfred Hitchcock.
Noir -- Usually applied to movies with dark lighting and darker outlook, a particularly bleak variety of hard-boiled crime story, where everyone is a villain, betrayal is inevitable, and frequently no-one is left standing at the end.
Police procedural -- A sub-genre focusing on the work of a team of police officers, usually investigating more than one case simultaneously, and traditionally emphasizing the technical aspects of investigation. Modern police procedurals often develop the characters and interactions of the police in great depth.
Red herring -- A "clue" that leads the detective on a wild goose chase away from the real perpetrator (from the practice of anti-foxhunting protestors dragging smelly fish across the trail to distract hounds from pursuit of the fox).
Romantic suspense -- Something of a hybrid between mystery and romance, with an adventurous heroine and stalwart hero who together solve a mystery and fall in love. Well-known writers of this form include Barbara Michaels and Mary Higgins Clark. Usually not part of a series.