Okay kiddo, imagine you have a bunch of cubes that are all the same size. A cubic ton is like a really big box that can hold a whole bunch of those cubes. In fact, it can hold exactly 35 of those cubes!
Now, it might not seem like a big deal to be able to hold 35 of these cubes, but these cubes are really, really heavy - they weigh about a ton each! That means that when you fill up this big box with 35 of those cubes, you have a whole lot of weight.
A cubic ton is a way to measure that weight, and it's equal to 2,000 pounds (which is also the same as one ton). So if you fill up this big box with 35 of these super-heavy cubes, you have a cubic ton of weight in there.