Accuracy refers mainly to the ability of language students to make a correct use of the grammar they are studying or have studied. By extension, however, it must also include other aspects of language learning, such as pronunciation, etc. Progress in this context is often measured by written tests as the main measure of competence.
One of the indirect consequences of concentrating on accuracy as a goal in a foreign language is that it is often difficult for students to transfer their theoretical knowledge of the language they are studying into the fluency needed to talk about themselves, for example, in a real-life setting.
Furthermore, excessive concentration of accuracy may result in speech on the part of the student which is quite accurate but exceedingly slow. This can irritate native speakers who would generally much prefer to deal with speech which is a little inaccurate but reasonably paced than speech with is slow but grammatically more sound.