Okay, so let's pretend that you and I made a deal to trade our toys. You promised to give me your favorite teddy bear in exchange for my new coloring book. This is called a "contract" because we agreed upon certain things that we would do.
Now, let's say that after a few days, you decided that you didn't want to give me your teddy bear anymore. Maybe you got a new toy and you like it more, or maybe you just changed your mind. But if you don't give me the teddy bear, you are breaking our contract and that's not very nice.
However, there is something called an "efficient breach of contract" that some people might think is okay. This means that even though you are breaking our contract, it might be better for both of us in the long run.
For example, let's say that you found out that your teddy bear is worth a lot of money and you could sell it for a lot of coins. You could then use those coins to buy new toys that you really want. And if you don't give me the teddy bear, I might be sad for a little while, but in the end, I might be able to find another cool toy that I like even more than the coloring book.
So while breaking our contract is not really a good thing to do, sometimes people might think it's okay if it leads to a better outcome for everyone involved.