https://www.cnet.com/news/2018-iphone-missing-adapter-headphones-ios-12-code-dual-sim-iphone/

The iPhone 7 Plus will not only come with Earpods with a Lightning connector, but they will also have a dongle (Lighting to 3.5mm analog adapter). The dongle allows you to use headphones with an analog headphone jack.

If the rumors are true, you'll be losing that dongle before you open the box of this year's iPhones. According to a Barclays report note published by MacRumors Apple will not include a Lightning-to-3.5mm Headphone Jack Adapter in the box of the 2018 iPhones. The company has included this dongle free of charge since it removed the headphone jack on the iPhone 7 and iPhone 7 Plus.