Imagine there's a big, fluffy blanket covering the ground outside, and under that blanket is where the rocks and dirt live. Each layer of the blanket is a different type of rock, like sandstone or limestone. Sometimes, certain layers have more rock than others, and we call those layers beds. So when geologists talk about beds, they're really talking about how the rocks and dirt are layered underneath the ground.
Just like how you might sleep on different types of sheets or blankets, the Earth has layers of different types of rocks and soil that make up its bedrock. These layers can give clues about the Earth's history and what kind of environment existed millions of years ago. So, when geologists study beds, they're actually learning a lot about what the Earth was like a long, long time ago.