Accuracy vs. Precision
What is the difference between accuracy and precision?
Accuracy refers to the closeness between measurements and their expected or true value (The farther a measurement is from its expected or the true value, the less accurate it is.)
Precision pertains to the closeness of measurements to one another.
One way that you can think about this difference is in relation to how an archer would aim their arrow. If "on the average" arrows hit the bulls eye then the archer will be considered as accurate, and if all the arrows hit "close to each other" then the archer will be considered as precise.
Precise measurements are not necessarily accurate (see the bottom left image) , and accurate measurements may not be precise (see the top left image).