Okay, so this is about how doctors know what kind of problems people can have when they are trying to sleep. Sleep is really important for us to stay healthy and strong, so it's important that doctors know how to help people with sleeping problems.
To make it easier, they made some categories. Categories are like different groups of things that are similar.
The first category is called Insomnia Disorders, which means that people have a hard time falling asleep or staying asleep. This might be because they are worried or anxious.
The second category is called Sleep Related Breathing Disorders, which means that people have a hard time breathing while they are sleeping. Sometimes they might snore or have pauses in their breathing which can cause them to wake up.
The third category is called Central Disorders of Hypersomnolence. This means that people feel very sleepy during the day, even if they slept enough the night before.
The fourth category is called Circadian Rhythm Sleep-Wake Disorders, which means that people have a hard time sleeping when they are supposed to. Their body might think that it's still daytime when it's actually nighttime.
The fifth category is called Parasomnias, which means that people do things while they are sleeping that they don't remember when they wake up. This can include things like sleepwalking or talking in your sleep.
The sixth category is called Sleep Movement Disorders, which means that people move a lot when they are sleeping. This can include things like restless leg syndrome or periodic limb movement disorder.
So, these categories help doctors know what kind of sleep problems people might have and how they can help them get better sleep. Does that make sense?