Show and tell

Show and tell is a common expression.  It is about showing an audience something and telling them about it.  

This group exercise is used to teach young children the skills of public speaking.Ammer, Christine. (1997). "show and tell," The American Heritage dictionary of idioms, p. 580.  For example, children will bring an item from home and will explain to the class why they chose that certain item, where they got it, and other relevant information.

History
The modern usage of this term began in the 1940s, but the general concept is older.  For example, in one of William Shakespeare's plays, a character uses the same words to link something with words explaining it'
 "... for if he show us his wounds and tell us his deeds ...."
 — Coriolanus, Act II, Scene 3Bulman, James C. (1985),  The Heroic Idiom of Shakespearean Tragedy, p. 20, citing  Coriolanus, Act II, Scene 3, line 1429.

 References

Category:Figures of speech
Category:Education