Focus

the coin here is NOT in focus : 

THE COIN LOOKS BLURRY

the trick is to press your finger on the screen where the subject is (whether it’s a cat or a coin)

This is better:

The phONE IS IN THE SAME POSITION, BUT I PUT MY FINGER ON THE SCREEN WHERE THE COIN IS

It's better in the second photo (but still not great because it's indoors and there's not much light) 

When there's abundant daylight, the focus becomes superb. 

And this is what we aim for. 

Here's another example

Before

After

COIN IS IN FOCUS! MUCH BETTER!