Gesture drawing consists of "quick, fluid strokes" drawn to convey the basic shapes of objects and how they relate to one another. There is no erasing involved and a gesture drawing should truly be a quick sketch.
Structural drawings are a bit more detailed, focusing on perspective (mine need work in this area!) and proportion. They are more finely-tuned than gesture drawings, and the eraser can be used liberally in completing the sketch.
Based on that description, can you tell which is which?
