Percent error is a measure of how far off or how precise/accurate your answer is compared to the actual answer.
The formula for percent of error is very similar to the formula for percent of change. One key difference between percent error and percent change is that percent error can NOT be negative, while percent change can be negative because it shows us that the value decreased. Percent error is just asking how far away was the estimate from the actual value. It does not matter whether it was more or less than the actual value.