Just a thought, “What’s the difference between maxi length, midi length and evening length dresses? And why is it important?”
Here’s a nice little graphic (click it) borrowed from the Vogue Sewing Book (the Vogue Bible) that answers that question.
The hemline is an important aspect of any garment and while the purpose of the hem is to help the garment hang well a hem also changes the silhouette and proportion of the garment.