With phone manufacturers trying to save space to make phones smaller, they are reducing the number of ports on a phone to just one USB C port. This means that adapters have to be purchased in order to use accessories etc. 
The USB C passive stereo earphones with MIC allows you to connect earphones to a phone/tablet etc that have USB type C ports only to enable telephone calls.
These earphones are designed for devices that have a USB C port only , older phones that have a 3.5mm port as well as a USB C port, it will default to the phones speaker.

USB Type C Stereo earphones with MIC
Passive
Volume controls
Ergonomic earbud design