First, you should hang your skirt on a dressform or on a "model". Then, you need to decide how long (or short) the skirt will be; this will be your hem point. The method I have used requires a yardstick and a rubberband: you sit or kneel on the floor holding the yardstick upright (the 36" mark at the bottom on the floor & the 1" mark at the top); wrap the rubberband around the yardstick at the point where the hem of the skirt is to be (for example, at the 12" mark); next, have your "model" turn bit-by-bit as you mark or pin at the hem point around the circumference of the skirt; if you are using a dressform, you will need to either turn the form manually or crawl around the form yourself. This method will give you a hem that is always level with the floor. I have included the URL of a manufactured device that works the same way as above. http://www.newarkdress.com/n107.html It is helpful to have your model or dressform elevated from the floor for your comfort.
A skirt's edge is called a Hem
Yes it is called a hem.
Hem.
Trumpet skirt
hem
Beach
Hem.
Sweep: You will see this measurement most commonly found on coats or jackets. The sweep is the circumference of the bottom hem of a skirt, dress, coat, or jacket. For a jacket or coat, measure the sweep across the bottom hem from open edge to open edge. For a skirt or dress, measure the sweep by laying the garment flat with seams matched, measure end to end, then double.
re-hem
Yes, to if you want the hem to be stiff you can either sew a hoop into it or (depending on the stiffness desired) starch it.
This is called an asymmetrical hem, or a high-low skirt.
Example sentence - She cleverly hid the diamonds in the hem of her skirt.