Okay so, you know how we talk to people and they understand us, right? And we can ask them to do things for us like bring us a snack or turn on the TV?
Well, imagine talking to your computer or your phone like you talk to a person and it can understand you and do things for you! That's what a natural-language user interface is.
It's like having a friend who is always listening to you and can do things for you whenever you ask. You just say what you want, and the computer or phone knows what you mean and does it for you.
This is really helpful for people who have a hard time typing or reading on a screen. It also makes things faster because you can just say what you want instead of typing or clicking on buttons.
So, let's say you want to ask your phone to send a message. Instead of opening the messaging app and typing the message, you can just say "Hey phone, send a message to mom that I love her". And your phone will do that for you!
It's pretty cool, huh?