It is a sad fact that no 2 items measure alike, even in a store. This is doubly true on Ebay, where people are selling things because the item is generally flawed in some way. It did not fit properly, it has some blemish like a seam going the wrong way, or a small stain somewhere... or the manufacturer themselves dumped the product line because it couldn't sell. Whatever the reason trying to figure out sizes is hard enough without having several different categories to choose from. I am attempting to put this into an easier reference guide.
most club clothes are juniors size. this means they are made for smaller sizes generally, and tend to be lower rise, shorter hemlines, cropped to the waist or midriff rather than hip length, etc. sexier is the way to describe them that comes first to mind. these are not your mama's clothes. these tend to be clothes no teenager's mama would allow them to wear in all honesty. brands of juniors clothes include things carried by Hot Topic, whole stores like DEB Shops, Rave, Aeropostale, etc. or in clubwear sections. tighter fitting, for slimmer figures.
business wear, longer length tops, higher rise jeans or relaxed fit pants, longer skirts (more just above the knee than mini), and looser fitting items in general. if you are short or skinny this type will not fit you. generally this refers to more conservative or frumpy clothes, things you wear to church or an office job, or if you have a curvier figure/are heavier. calf length skirts, suits, etc. JC Penney's or Sears, or most lower-end department stores like Target or Wal Mart have much larger misses sections than anything else.
PLUS or WOMENS:
they keep changing the name for politically correctness, but this means larger sizes. i get so frustrated when skinny little girls list stuff for sale as plus size and it's a size 10. plus means size 18 and over, generally 40 inch waists and up. looser fitting, made for curves and larger frames. longer lengths as well. Torrid, Hot topic's sister company, has started making more trendy clothes, bigger versions of the club clothes they normally sell at Hot Topic. there are options out there, but ask any seller for measurements before you buy. Lane Bryant, Fashion Bug Plus, are store examples.
* In short there is no industry standardization for sizes. Size charts are generally useless. Measure an item of yours that fits you the way you like, (measuring yourself tends to come up with larger numbers than the inches in clothes you need, I don't know why but it's true) and then compare the measurement you get from your item to the measurement in the description. If the seller does not provide measurements, ask before bidding. tape measures sell for under $2 in the laundry detergent/soap aisle of your local supermarket. There is no excuse not to have one.
Low Rise: fits on the hips or just above them, not at the natural waist. distance from the crotch to the waistband is smaller than on other styles. generally the hip and the waist measurements are the same number, because the hip is where the waist is resting.
Normal Rise/Classic or High waist: fits at the natural waistline. generally the waist measurement will be smaller than the hip measurement, so ask for both. the distance from the crotch to the waistband will be larger than with other styles.
mid rise: sits just under the belly button. a compromise between the low rise juniors style and the high waisted classic misses style, this has a medium distance between the crotch and the waistband. waist will be a smaller number than the hip measurement, so ask for both.
mini skirt: generally between 12 and 15 inches from the waistband to the hem
above the knee skirt: generally from 15 inches to 18 inches from the waistband to the hem
Inseam: the distance from the crotch to the cuff of the pants, in inches, on the inside of the leg.
waistband measurement: flat across in inches, take that and double it. 17 inches flat across = 34 inch waist.
In closing, always ask for measurements before bidding. Check out the item and its description carefully to avoid getting the wrong item. Size conversion between Juniors and Misses is especially messed up, there really is no perfect conversion. If you are skinny and want sexier tighter fitting stuff, get Juniors. If you have curves or want to look more professional or conservative, get misses sizes. if you are larger, get plus sizes. a Junior's 13 is roughly the same as a Misses 14. the sizes aren't really all that different in inches, it's where they sit on your body that makes the difference.