Accuracy
Accuracy refers to the agreement between experimental data and a known value. You can think of it in terms of a bullseye in which the target is hit close to the center, yet the marks in the target aren't necessarily close to each other.
Precision
Precision refers to how well experimental values agree with each other. If you hit a bullseye precisely, then you are able to hit the same spot on the target each time, even though that spot may be distant from the center.
Keep in Mind
Data can be very precise such that each data point is close to the others, yet contain a high degree of experimental error.
