Bandwidth is like a road for information to travel on the internet. Just like different roads have different amounts of lanes, bandwidth is how much information can travel on the internet at one time.
So, imagine you have a toy car and you want to drive it from your house to your friend's house. If there's a big, wide road with lots of lanes, you can drive really fast and probably get to your friend's house quickly. But if there's a narrow, small road with only one lane, you'll have to drive slower and it will take longer to get to your friend's house.
In the same way, if you have a lot of information like a video or a big file that you want to send over the internet, and you have a lot of bandwidth, it can travel quickly and easily. But if your internet connection has less bandwidth, it will take longer for that information to get to where it needs to go.
So, basically, bandwidth is how much information can travel on the internet at one time, and having more of it means things happen faster!