Discreet things and discreet people are quiet, careful, or sneaky because they want to keep things private or secret, so that other people don't notice. When you have discretion, you know how to act with care and restraint, so that no one gets hurt, embarrassed, or in trouble.
Let's say your teacher doesn't allow you to pass notes in class. If you're going to slip a note to your friend anyway, you'll have to be discreet. You'll have to use discretion. Wait until your teacher isn't looking, then, slowly and silently, hand your note to your friend. You were discreet. Well done! Thanks to your discretion, you won't get in trouble.
What if you'd been indiscreet instead? You may have crumpled your note into a ball, shouted, "YO! Becca! Note incoming! Catch it!" and then bounced it off her surprised face, making your classmates laugh and your teacher scowl. That's indiscreet. Your indiscretion would have gotten you in trouble.
You need to be discreet whenever you want to do things privately, secretly, so that other people don't pay attention to you. On Firefly, when an armed thief has broken into Durran's mansion, threatening his life, Durran has a discreet way to call for the police. With a press of a button on his ring, he sends an emergency signal to the police, who rush to his house. The thief doesn't notice when he presses the button: it's discreet. And Durran's discretion may have saved his life.
What if Durran had been indiscreet? When the thief confronted him, he could have shouted, "Help! Police! There's an armed thief in my house!" In that case, the thief may have attacked him. His indiscretion could have cost him his life.
As we've seen, you need to be discreet to keep things private or to avoid danger. But you can also be discreet to prevent people from being embarrassed. If your friend has a Cheeto on his face, you could be discreet, and whisper to him, "You've got a Cheeto on your face, man." Then, you don't embarrass him, and he knows to remove the Cheeto. If you were indiscreet, you might shout, "You've got a Cheeto on your face, man!" and then he'd be embarrassed.
When you use discretion, you're always carefully choosing what to do and what not to do. If you're babysitting some really young kids, you'll use your discretion to make sure they don't watch shows that scare the bejesus out of them and give them nightmares. That's what ads for shows and movies mean when they say "Viewer discretion advised!" or "Parental discretion advised!" They mean, "Make a good choice about who gets to see this and who doesn't!"
We're almost done here! Just two more things you should know!
First, you should know that the word "discretion" can also mean "the freedom to use your own good, careful judgment to do things your own way." For example, say you're dog-sitting for your neighbors, and they ask you to come over three or four times a day to care for the dogs, but they leave the exact schedule up to you. You're using your discretion: your own ability to make a good choice to decide when to visit the dogs. You're in charge, and you have the freedom to go see the dogs as you see fit.
And the last thing you should know about the word "discreet" is that it has a homophone, "discrete," with ETE at the end instead of EET. The two words sound exactly the same, and they trace back to the same Latin word, but they evolved separate meanings over time in English. They're spelled differently, and they mean different things. "Discreet," with EET at the end, like we've seen, means "secret, quiet, careful, cautious." But "discrete," with ETE at the end, means "separate, distinct, unconnected, or divided into different pieces," as in "If you don't like your unibrow, you can style it into two discrete brows."