Some employees are guilty of coffee badging, or even jiggling their mouses to look active while working remotely. But even when they’re being productive on the job, there are a few tasks that could be considered “fake” work—at least according to Slack cofounder and former CEO Stewart Butterfield.

“Here’s my grand theory: Hyper-realistic worklike activities goes along with this other concept called known valuable work to do,” Butterfield recently said on Lenny’s Podcast. “Hyper-realistic worklike activity is superficially identical to work…But this is actually a fake bit of work, and it’s so subtle.”

Butterfield coined these two concepts, having seen the type of work that goes into scaling startups into big businesses. The serial entrepreneur cofounded photo-sharing platform Flickr in 2002, serving as its CEO for several years, before his next venture establishing and leading $26.5 billion giant Slack back in 2009. Butterfield has been keeping a low profile since he stepped down from the company in January 2023.

From his decades of experience in the business world, he’s separated workforce productivity into two separate camps: hyper-realistic worklike activities, which he deems as “fake” work, and known valuable work, which promotes innovation and strengthens success.