Cartoon Porn vs. Hentai
The two get lumped together constantly, but they come from different art traditions. Hentai refers to Japanese anime-style erotic art and animation with its own visual conventions. 'Cartoon porn' usually means explicit content drawn in a Western animation style - closer to what you'd see on American TV cartoons or comic books - frequently featuring recognizable characters from existing shows, games, or films reimagined in explicit scenarios. It's essentially adult fan art applied to Western pop culture rather than an original Japanese-derived aesthetic. Some sites blend the two traditions, applying an anime-influenced art style to Western characters, but the distinction between 'cartoon' and 'hentai' tags still holds up as a useful sorting line for most fans.
Where Rule 34 Comes In
You'll see the term 'Rule 34' used constantly in this space. It comes from an old internet adage - 'if it exists, there is porn of it' - that emerged from image-board and forum culture in the mid-2000s as a joke about how thoroughly the internet sexualizes any popular character or franchise. It stuck around as shorthand for the entire genre of character-based fan porn, cartoon or otherwise, and most cartoon porn sites are essentially organized around that same impulse: take a well-known character and put them in an explicit scene. It's become such a recognizable piece of internet culture that plenty of people who've never visited an adult site still know the phrase from general online jokes and memes.
Terminology You'll See
'Parody' is used loosely here to mean any work based on existing characters, regardless of whether it's making fun of anything. 'Toon' is common shorthand for cartoon-style art generally. You'll also see 'comic' or 'animated' used to distinguish static panel art from actual short animations, since sites in this category host both. Artist credit matters a lot in this community - much of the content is commissioned or independently produced fan work, so recurring artist names and studios carry real weight among regulars, and requests for a specific artist's take on a character are a common form of engagement.
Why the Genre Persists
A huge amount of it comes down to nostalgia and familiarity - putting a character people already have an emotional attachment to into an explicit context creates a kind of fantasy shortcut that original characters don't have. It also benefits from an enormous, constantly refreshing pool of source material: every new show, game, or franchise that gains a following almost immediately generates its own explicit fan art, which keeps the genre supplied with new content without needing new formats or gimmicks. As animation and gaming fandoms keep growing generation after generation, the pipeline of new characters feeding into this space effectively never runs dry.