Lifestyle creep is when you start to spend more money on things that you don't need as you start to make more money. It's like when you get a bigger allowance or start making more money from your job, you might be tempted to spend it all on new toys or candy or other things that you didn't have before. As you get older, this can happen with things like clothes, gadgets, or fancy dinners. This can be a problem because spending more money on unnecessary things can make it hard to save up for important things like a college education, a down payment on a house, or a rainy day fund. It's important to manage your money wisely so that you can enjoy the things you need and save for the things that really matter.