NFC (near-field communication) makes it easy to securely share with sources you trust, without having to type a lot of information or struggle with pairing.
Most users keep NFC on for easy payments. It uses little battery. Turn it off when not needed to avoid unwanted connections and reduce security risks.
Open quick settings and tap 
Or, go to Settings > Connected devices > Connection preferences.
Tap NFC and turn it on 
If you don't see this option, then your phone doesn't support NFC.
To know whether NFC is on by glancing at your status bar:

When NFC is on, you'll see 
Open quick settings and tap 
Use NFC to pay quickly and securely at payment terminals by touching your phone to an electronic reader.

Tap Contactless payments and adjust settings:
Open quick settings and tap 
Some businesses include NFC tags on terminals or displays, so you can tap your phone as proof of entry - to get into events or onto public transportation. Organizations also use NFC tags to provide information, such as maps, product info and more.
Look for the NFC logo on displays, signs, or terminals.

This is different than the logo for contactless payments.
Hold the back of your phone within 2 cm of the logo until it scans the tag.
If nothing happens, slide your phone slightly up, down, or sideways on the tag and try again.
After each troubleshooting step, check to see if the issue is fixed.