Back in the days of kayfabe, there were two types of people you'd encounter at professional wrestling events: "marks" and "smarts". Marks were the folks who paid to see the show they thought was an actual athletic competition. On the other hand, smarts were people who knew the truth about wrestling, that it was a staged athletic exhibition with no real competitive aspects. Usually, smarts had a connection backstage to wrestling, and most of them worked either for or with a promotion.
As the truth about pro wrestling became more widely known, a self proclaimed third class of people came into being in between these two: the smart mark, or "smark" for short. Smart marks knew the whole thing was staged, but enjoyed it anyway. They tended to look to different things in a match than marks did; while a mark would like a wrestler mostly based on how they behaved, a smark would like a wrestler more based on their in-ring performance. When a smark gets caught up in the moment and reacts to a spot as if it were real, this is known as "marking out". Many smarks consider it a sign of a truly great match that it can make them mark out. Nevertheless, smarks did not have any real connections backstage; they simply enjoyed the show.
These days, since the vast majority of the pro wrestling fanbase tend to fall into the smark category under the old definition, the definitions have mutated somewhat. Now, marks are the people who follow wrestling casually and tend to care more about the drama and the stories than the actual construction of the match, and smarks are the people who study and analyze matches, root out backstage gossip, and generally take wrestling more seriously. Few marks have enough knowledge of the business to self-identify as marks; indeed, the term is more often thrown about by smarks as an insult. Another perception is that "smark" is an incorrect term and shouldn't be used. Connection with the business is required to be a smart, ergo, no one who isn't in the business can be anything other than a mark. Of course, as the Internet gets bigger and more wrestlers, especially independent ones, develop an online presence, some have become more receptive of the term. On the other hand some use "smark" the way smarks use mark, Kevin Nash called them the biggest marks of all "because you get to work them twice, once on TV and once in the sheets." "Sheets" (or "dirtsheet", "scandal sheet", or "ragsheet") refers to publications (now websites) like The Wrestling Observer Newsletter that provide this inside dirt, though today such insider news can be found on ESPN and even places like Forbes and Varietynote .
It used to be an axiom that smarks and marks did not get along. Nowadays, factoring in the ever growing gray area between the two, it's really not that bad. Many marks are capable of saying "Wrestler A's matches bore me, I take a bathroom break when they're on", and many smarks are capable of saying "so what if Wrestler B isn't technical perfection in the ring, they entertain me". The advent of the Internet has allowed the two communities to mingle as they didn't back in the days of the newsletters and video tape trading, and the line between smark and mark, such as it is, has blurred significantly. The negative perceptions on both sides of the divide come from the extreme edges of both camps. The smarks who nitpick matches half to death looking for trivial flaws so they can rate popular matches "DUD" on the 5 star scale and feel intellectual, and the marks who shrilly accuse anyone who criticizes a show they like (say, WWE in general) or favorite wrestlers (John Cena, Roman Reigns, etc.) of being know-it-all smarks.
Although smark is still exclusively a professional wrestling term, similar groups have emerged in other forms of entertainment. For example, there are people who will watch a TV show, enjoy it, and leave it at that. However, there are other fans of a show who delve into the online community, especially entertainment news and "spoilers" about shows. In this instance, a "mark" would sit and anticipate if a sick character is going to get better, whereas a "smark" would go online, find out that the character's actor is considered horrible to work with, notices his contract is expiring soon, and realizes the character probably isn't going to get better.
- Parodied in Burst Angel; when a league combining wrestling with Kamen Rider is interrupted by the performer in the monster suit actually turning into a monster, one kid watching is just non-plussed that the promised "power-up" didn't look like it did in the promotional materials. Later, the audience applauds the performance when Jo starts wreaking havoc.
- Gosalyn of Darkwing Duck fits the description: when Darkwing takes part in a charity benefit wrestling match and she cheers him on with advice, he reminds her that wrestling is fake. She replies "Of course it's fake, the fun part is pretending it isn't!"