What does a 5% level of significance mean?

Sure. In other words, a 5% significance level corresponds to a 95% confidence level, which implies that you are 95% certain that an impact is being signaled.

It sounds challenging. Could you perhaps provide a little more detail?

The significance level, which is frequently represented by the symbol, indicates the likelihood of making a Type I error. If you reject the null hypothesis when it is true, there is a 5% chance that you did so at a significance level of 5%.