The way this word is defined in education varies.
It is when two students perform an activity (e.g., a dialogue), and the other learners observe.
An open question is one which could be answered in many different ways, not just 'yes' or 'no'. Open questions begin with wh- question words, or how. See closed questions.
See Situational English.
organs of speech
Organs of speech are also called articulators. They are the parts of the body used to produce spoken language - lips, teeth, the various parts of the tongue and the roof of the mouth: alveolar ridge, hard palate and velum (soft palate). They also include the uvula and the glottis.