A comic that only has one issue (a self contained story) is a One-Shot or 1-Shot. These are typically 24–48 pages in length and contain an entire story from beginning to end.
One-Shots are industry standard when the publisher or creative team wants to test the market to see how the reception will be for a particular title.
One-Shots are also used when dealing with a finite subject matter. Examples include Celebrity or Biography comics. In the 1990’s these were very popular, and they put out One-Shots for Red Hot Chili Peppers, The Cure, Pete Rose and other music and sports personalities.
When a one-shot is popular or gets enough notoriety, it can often turn into a mini-series or even an ongoing series.
Another form of one-shots that evolved in the 1990’s were Issue #0’s and sometimes #1/2’s. These were often stand alone stories, involving the main characters set in an alternate time frame or setting, outside of the ongoing series’ continuity. Like the one-shot, they typically told a complete story from beginning to end.
The version of the one-shot with the most pedigree, however, was the Annual. You can find annuals from many of your favorite series dating back to mid century. The idea was to put out a stand-alone issue, once a year, of around 48–100 pages. These were likely gave way to today’s “graphic novel.”
Another version of the “Annual” was the Giant Size that marvel was well known for. These were complete stories from beginning to end. Giant Size X-Men #1 was probably one of the most acclaimed “Giant Size” releases of the 20th century.