A trundle bed is a low bed on wheels that rolls under a regular bed when not in use, then pulls out when you need an extra place to sleep. Think of it like a bed drawer: during the day, it's hidden away, but when a friend sleeps over or a cousin visits, you can roll it out and suddenly you have two beds in the space where one used to be.

Trundle beds are clever space savers, perfect for smaller bedrooms or when siblings share a room. The bottom bed sits so low to the ground that it fits neatly beneath the taller bed frame above it. The wheels make it easy to trundle (roll smoothly) in and out, which is where the bed gets its name.

Many families use trundle beds in guest rooms or children's bedrooms. A kid might sleep on the main bed every night, then pull out the trundle when a friend comes for a sleepover. In the morning, the bottom bed rolls right back underneath, and the room is clear again for playing or doing homework. It's like having a secret extra bed hidden in plain sight.