What is the difference between accuracy and precision?

In a strictly technical sense, accuracy is a measure of how close a result is to the "true" value. Precision is a measure of repeatability.

In reality, it is often the case that the "true" value can never be known and as a consequence these terms are often used interchangably.

It is possible for measurements to be accurate and precise, inaccurate but precise, accurate but imprecise or inaccurate and imprecise. When establishing standardised test methods scientists attempt to ensure that the measurements are both accurate (i.e. close to the true value) and precise (i.e. highly repeatable).