This seems to be a well kept secret. Not many people are making use of the big potential of NFC tag, card or sticker.
There are a lot of things we can do with NFC Tags. They are relatively cheap. I bought mine from Amazon for $14 for 12 pieces. These are not plastic card but small round stickers. You can get these in black , white or colours.
So what do you do with these. You can use NFC stickers to store information, in very small chunk for the iPhone to read. Better still you can tap the iPhone on the NFC sticker to automate some actions that you program. With the shortcuts function in iPhone, there is so much you can do without buying 3rd party app. All you need to invest is just slightly over $10 to start home or personal automation.
A very useful and practical example is to send a pre-programmed text message to your family by tapping the iPhone while driving to tell them that you are only half an hour to arrive home. Imagine that you transfer your business card to another person just by asking them to tap the NFC sticker on your wallet or briefcase. The iGeeksblog has some good examples of the use case.
There are a lot of free references you can get from the Internet. This article from Mashtips is one of the best.
The technology is not unique to iPhone. You can even do more with Android devices as the system has less restriction.