CYOA is the commonly used acronym of choose your own adventure. In the past this refer exclusively to the books that sent you to various pages dependent on your choices. Concept wise, this would work really well using hyperlinking but despite that it never really caught on with the digital generation. No, in recent years choose your own adventure has come to refer to a series of choice games that look more like a would you rather or character creator for RPGs and Video Games than anything else.
At their core CYOAs always provide a series of choices often accompanied by a scenario. You've been chosen completely at random to be savior of a generic fantasy world, choose your magic item. A wizard is retiring and has decided to leave you one of his grimoires. You're about to spend ten years trapped in a room, what will you take with you? Etcetra. If some random person's list of options isn't enough to interest you most CYOAs go to the trouble of including art borrowed from where ever they can find it to make the options really come alive.
Almost all CYOAs are an image file or series of image files. They have a thriving subreddit as well as never ending threads on sites such as Space Battles, Sufficient Velocity, and other sites designed to keep nerds away from general society.