The nature of standing waves 

• The principle of superposition yields a surprising sum for two identical waves traveling in opposite directions.
• Snapshots of the blue and the green waves and their red sum shows a wave that appears to not be traveling.
• Because the resultant red wave is not traveling it is called a standing wave.

Nodes and antinodes 

• 
• The standing wave has two important properties.
• It does not travel to the left or the right as the blue and the green wave do.
• Its “lobes” grow and shrink and reverse, but do not go to  the left or the right.
• Any points where the standing wave has no displacement is called a node (N).
• The lobes that grow and shrink and reverse are called antinodes (A).