Stephen Hillenburg, a former marine biologist who became an animator and went on to create “SpongeBob SquarePants,” has died at 57. Read the Times’s full obituary here. This explainer was originally published in May when “SpongeBob” was nominated for 12 Tony Awards.

“SpongeBob” and its titular character made their debut in 1999. The show has aired on Nickelodeon for nearly two decades. In the nearly two decades since, Mr. Hillenburg’s work has been spun into a Broadway musical, a number of video games and two films. A third film is also scheduled to be released in 2020.

The yellow sponge in rectangular pants has also been at the center of online meme culture for a generation who grew up as the internet came into its own.

If you’re not in that generation, or if you’ve been living under a rock, you may have missed the continued cultural relevance of SpongeBob. We’re here to help.