An explanation helps all parties understand why something went wrong. By offering an explanation, you’re saying, “This thing happened because Y. It’s my fault Y happened. I’m not sure how I didn’t see that coming. In the future, I will do X and Z to make sure Y never happens.”

That is a great explanation and something everyone wants to hear after they catch a mistake you made. You’re accepting the responsibility for the mistake and explaining why it happened.

An excuse helps whoever made the mistake feel better about themselves. They blame Y, not their lack of foresight to predict Y and prevent it. When you offer an excuse, you say, “Y caused this thing to happen. I was working an A and B so I couldn’t also work on Y. Who was supposed to be working on Y?”

One accepts responsibility; the other shirks it.

When you make a mistake, don’t be afraid to explain what happened. People—especially bosses—like to know why things went wrong.

Just be careful not to offer an excuse.