Webcomics are comics that are on the internet, it’s as simple as that. Traditional webcomics release one page or strip at a time and are available to read for free, although variations on this concept definitely exist. More so than traditional comics, webcomics vary wildly in style, content, and quality due to their low barrier to entry (basically none – you don’t even need to be an artist to do a webcomic, although it can help). As such, webcomics are definitely subject to Sturgeon’s Law: “90% of Everything is Crap”. Fortunately, there are a lot of ways around this – most commonly by only reading popular, established webcomics. Of course, there are plenty of unrecognized gems that can be found if you’re willing to dig around. The best thing about trying out lots of new materials with webcomics is that they’re free – so all you waste in sorting through several bad webcomics is time (and often not that much, as most bad webcomics make themselves painful obvious really quickly), and if you find a really good comic, well, that effort was definitely worth it!
One of the best things about web comics is that there is a very minimal "barrier to entry" for creators. They don't need to convince a publisher to put out their comic. They don't need to pay a printer & figure out how to distribute the comic if they are going the self-published route. They need a computer and some rudimentary tools and it's fairly easy to get their material up on the web.
These run the gamut from short gag strips to short strips set within a larger continuity to longer narratives telling fully realized stories. As usual, Wikipedia is a great source for the history of webcomics.
Webcomics are free, and many of them easily rival or exceed the quality of print comics. That killer combination of free and great is what makes them so amazing. Since webcomics update over time and their authors are usually easily accessible, many webcomics have great fan communities with whom you can speculate about the latest developments or swap jokes with.
Think of a premise, there’s probably a webcomic for it. Several sites catalog webcomics, which can be quite useful as there are literally tens of thousands of them (according to Wikipedia, 38,000 as of 2007, and that number has no doubt risen since then).
Webcomics typically fall into a couple of broad categories:
There are of course plenty of other comics, like slice of life comics, or even autobiographical ones, but the majority are either story or gag comics. As for genres, you can find many examples in almost every genre, but humor is prevalent, especially as it relates to pop culture and gamer culture. Even serious strips often have relatively high amounts of humor in them.
Part of this stems from the nature of how most webcomics update. Since webcomics give you the story little by little, page by page over a long period of time, jokes and humor can help keep people entertained instead of waiting for long, slow payoffs. Then again, not every webcomic follows that format, but it’s definitely a noticeable trend.
Recommendations of friends with similar tastes to yours and reviews by people with generally excellent taste (such as the ones you’ll find on this very site) remain the best way to find good webcomics. However, they’re far from the only option.
Most webcomics support themselves based solely on ad revenue and voluntary purchases – branded merchandise, print re-issues of freely available online content, or kickstarter campaigns. Naturally most webcomics fail to turn much of, if any, profit and only a small handful can actually count themselves as professional webcomic creators.
It stands to reason then that if a webcomic has gathered the large number of fans needed to become self-sustaining it must have some great stuff – maybe not for your tastes, but definitely for someone.
Wikipedia provides this handy list of webcomic creators successful enough to keep their strips up on their merits alone. Almost all these comics are excellent and would make a great starting point for any new webcomic reader. Be sure to look at the comics that are self-reportedly self-sustaining as well. The creator’s finances are less important than the popularity (and thus, implied quality) of their comics.
A variety of sites devoted to cataloging and ranking various webcomics also exist. The aptly named TopWeb Comics is a good resource, ranking hundreds of webcomics by genre. The ranking on this particular site is handled by fan voting, so the rankings can change quite a bit, although in practice the popular comics tend to stay near the top while the less popular ones languish near the bottom. The rankings themselves aren’t the best measure of quality, but they can help and you can be assured that the comics aren’t going to be absolutely terrible. The site also provides content advisories for those sensitive to content.