Much like infant boxers, minicomics are small but can pack a mean punch. After reading what's available here, you may have an idea of what a minicomic is but, if not, here's some information for you.
Originally, minicomics were considered to be any comic book which falls within certain size guidelines, anywhere from 5.5x4.25" and smaller. While that's still true to a certain extent, the term "minicomics" has become more of a catchall description for any comics that are self-published amd simply smaller than traditional the comic book size, approximately 6.5x10.5".
Their popularity has increased in recent years, even going so far as to have a two industry awards dedicated to them. Isotope - The Comic Book Lounge annually presents the Isotope Award for Excellence in Mini-Comics and the Small Press Expo, a comic convention dedicated to small press books, issues an award for Best Minicomic of the Year as part of its Ignatz Awards ceremony.
While there is no official first minicomic, they first came to prominence in the 1980s with such creators as Matt Feazell and his comic, Cynicalman. Other minicomics creators of note would be the Dongery publishing group from Norway, John Porcellino and his King Cat Comics and, of course, FULL SANCTION!