Imagine you have a backpack with some crayons inside. You want to tell your friends that the crayons are in your backpack. In English, you might say "Crayons are in backpack." But, if you're talking to your mom, you'd probably say "The crayons are in MY backpack."
Did you notice the difference? The first sentence didn't have any extra words (like "the" or "my") to help show who the backpack belongs to. This is called "zero-marking."
In English, we use zero-marking when we don't need to add extra words to show who something belongs to or which one we're talking about. It's like a shortcut for when we don't need to be super specific.
So, when you hear someone say "Crayons are in backpack," don't worry! They're not forgetting words - they're just using zero-marking to save time and energy.