So what are comics?
Comics, like any other medium, are tricky to define. Scott McCloud - a comics creator and theorist - came up with the following definition in his book Understanding Comics:
Juxtaposed pictorial and other images in deliberate sequence, intended to convey information and/or to produce an aesthetic response in the viewer.
I've come up with my own similar, yet simpler (some could argue more imprecise) definition:
Two or more images, sometimes but not necessarily paired with words, used to tell a story or provide information.
The "sometimes but not necessarily paired with words" part is most important, since it includes comics not normally thought of as such - like airplane safety brochures and some instruction manuals - and excludes non-comics sometimes mistaken for comics, such as most picture books.
A simple litmus test is: "If you take the pictures away, and can still understand it, it's not comics." Most picture books, minus the pictures, still work as poems or short stories. Comics, on the other hand, become an incomprehensible jumble of captions and dialog. (Of course, there are some text-heavy comics that mess with the test. Like I said, it's imprecise!)
It's worth noting that most people consider picture-writing like rebus puzzles and hieroglyphics to not be comics, since they stand for sounds or individual words rather than whole thoughts or scenes.
(If you need tips on reading comics, check the How to Read Comics article!)
Where/When did comics first appear?
Now that is a question for the ages. Trying to pinpoint the first comic is like trying to pinpoint the first human - it's hard to tell exactly what you're looking for, and for some reason it's even harder for people who know a lot about it.
All we know is that early comics-like things date back to the beginnings of civilization. Picture-based accounts of history and mythology crop up everywhere from ancient Egypt to the Romans and Aztecs and beyond. In fact, given the dramatically lower global literacy rate, it's possible that "comics" were even more common in the past than they are today.
Skipping over several centuries of illustration and early cartooning (sorry, Rodolphe Töpffer,) the first comics that were widely called "comics" appeared around the turn of the 20th century with early newspaper strips.
In the days when most cities had multiple newspapers, competition was fierce, since it's hard to have a monopoly on facts (unless you make news up, which is a history lesson unto itself.) One way for papers to distinguish themselves - and sell copies to folks who wouldn't buy them otherwise - was to devote some pages to comic strips like Hogan's Alley and The Katzenjammer Kids.
After a while, publishers began repackaging comic strips into mini-tabloids of their own, like The Funnies. These inspired others to produce their own comic strip magazines, like Famous Funnies (widely considered the first comic book,) independently from newspapers.
Soon enough, publishers began printing comics in new genres, with adventure and science fiction stories quickly joining the pack. Despite these dramatic leaps away from pure comedy, the term "comic" stuck.