In chemistry, accuracy refers to the closeness of a value to its true value - its standard or known value. For example, if an experiment yields a product whose value is 5.6 grams and the true value should be 14.2 grams, then this experiment is not very accurate.
In colloquial use, accuracy and precision are often used interchangeably, but these words actually have two very different meanings. While accuracy refers to the closeness of a value to its true value, precision refers to the closeness of measurements to each other. If in the previously stated experiment, a second value of 5.2 grams is obtained, then the recorded values are precise, but not accurate.