Modular crate electronics is like having a bunch of Lego blocks that fit together to make different things. Each block is a little computer chip that does a specific job, and you can put them together in different combinations to make all kinds of cool gadgets.
Just like Lego blocks come in different shapes and sizes, the computer chips in modular crate electronics come in different types and sizes too. Some might be really good at sending and receiving signals, while others might be better at storing data or controlling motors.
The great thing about modular crate electronics is that you can customize your gadget by picking the specific computer chips you need for your project. If you want to make a robot that can walk and talk, you might use some chips that help it move and others that help it make sounds.
When you're done building your gadget, you can take it apart and use the same computer chips to make something totally different. It's like having an endless supply of Lego blocks that can turn into anything you want.