Gross speed is the number of keys typed converted into Words per Minute. It is a simple score showing how fast you were typing the keys. This is how fast you would type if you didn't make any mistakes.

Net speed is more interesting and useful as it gives your typing speed with errors calculated in the result.

Net speed can also be called Adjusted Typing Speed.

Usually, if a job opening has a typing speed requirement, it is for net typing speed, even if this is not specifically stated. Your typing speed after errors is what counts.