Judy Alter, the director of the TCU Press, answers the question "Just what is a university press?" for the Dallas Morning News:
University presses are academic publishers, ranging in size from small to very large. In Texas, we have at least 12 such presses – UT Press at Austin is probably the biggest, followed by Texas A&M University Press. TCU Press, for whom I work, is one of the smallest in the nation.
The joke used to be that university presses published academic works that sold six copies of any one book – to the author's mother. It's not true anymore. Scholarly presses have their eye on the general reading public. Economic necessity has dictated that most presses have to straddle that line between trade books for popular stores and academic books for a more limited audience.
Academic presses now publish some fine fiction. Back in the '70s, author John Kennedy Toole wrote a novel titled A Confederacy of Dunces. Whether it was depression over failure to publish or some other cause, Toole committed suicide, after which his mother practically browbeat Louisiana State University Press into publishing the book.
When he won a posthumous Pulitzer Prize, so many thousands of copies sold that, according to rumor, LSU decided the press no longer needed financial support, causing budget confusion in ensuing years without a blockbuster. But the fictional ice at university presses was broken.