Accuracy is how close the experimental results are to the expected result, which is usually a predetermined value. Precision is how often you get the same result or a result close to the results from the previous experiments. This value does not necessarily have to be accurate, meaning it can be a repeated value which is not close to the expected value. For example, on a scale from 1-10, if the expected value is 5 and all or most of the experimental values are 5, with a few close deviations like 3-4, you can say the results are accurate and precise. If you run the same experiment and most of the values are not close to the expected outcome but repeat or are close to each other, such as 8-9, you can say its precise but not accurate. If you run the same experiment and you get results which vary on a large scale, such as 2-8, you can say the results are neither precise nor accurate.