Four years after Snapchat’s launch, Chief Executive Evan Spiegel abruptly released a YouTube video Tuesday explaining how the app works and why people use it.

As part of a larger effort by Snapchat to explain its app to older non-users, Spiegel waxed philosophical in the video about generational shifts in photo taking and how Snapchat’s disappearing pictures are the next step in the evolution of images. His beliefs about photography’s changing role in society come from recent conversations with perplexed friends that have Snapchat-using children.

“They were so confused because they saw their children taking a zillion pictures a day. Pictures of things they would never take pictures of. It didn’t seem like their kids cared what they looked like,” said Spiegel. “That is really a great way to explain what Snapchat is.”

According to Spiegel, Snapchat’s disappearing photos can’t be viewed in the same way photos of the past were.

“Historically photographs have been used to save really important memories,” said Spiegel. “But today (because of) the advent of the mobile phone and the connected camera, pictures are used for talking. That’s why people are taking so many pictures on Snapchat today.”

Moreover, he said, on-demand photography has changed the nature of expression. Millennials no longer see photos as permanent.

“The mobile phone has really empowered this idea of instant expression,” Spiegel said. “Showing someone where you are and how you’re feeling at that moment.”

Now, everything is fleeting.

“I’m the result of everything of I’ve ever done, but I’m not the accumulation of everything I’ve ever done,” he said.

Spiegel may have some more explaining to do.

Technology reporter Garrett Reim can be reached at [email protected]. Follow him on Twitter @garrettreim for the latest in L.A. tech news.