Headpphone jack on my IPhone 7?

The iPhone 7 comes with an EarPods with a lightning connector. (The same port you use to charge the iPhone)

It also came with an adapter for older 3.5mm plug.

If you just purchased this iPhone it probably did not come with the adapter, you will need to buy one to use with wired headphones with a 3.5mm jack.

Wired earphones are so 20th century!

https://www.bose.com/en_us/products/headphones/earphones/soundsport-wireless.html#v=soundsport_wireless_citron

Wired earphones are so 20th century!

I like to think of it as "Wired earphones are so second millennium!"

:-))