font-size makes text bigger or smaller.

The style of the letters is called the font. font-size sets how big the letters are. The value is a number with a unit after it, like 24px, with no space between them.

px is short for pixel, one of the tiny dots of light that make up your screen. Ordinary text is 16px. An <h1> starts at 32px, which is why headings look big.

Make the important things big and the small print small. Around 12px is the smallest most people can read in comfort.

<h1>Big news</h1>
<p>The cat learned to open the fridge.</p>

h1 {
  font-size: 48px;
}
p {
  font-size: 20px;
}

Try 100px on the heading to see how far it goes.