Fluency refers to how well a learner communicates meaning rather than how many mistakes they make in grammar, pronunciation and vocabulary. Fluency is often compared with accuracy, which is concerned with the type, amount and seriousness of mistakes made.
A learner might be fluent (make their meaning clear) but not accurate (make a lot of mistakes).
In the classroom:
Activities that help to develop fluency focus on communication, for example discussions, speaking games, presentations, task work such as projects and e-mailing.