These are not different from your usual cotton tops in respect of length or design. However, when it comes to the clothing fabric used, it is lot more classier and expensive than a usual top. They are usually designed in fine fabrics such as velvet, satin, silk, etc. Besides, they are also adorned with sequins and other embellishments.
There is also slight difference in their fashion pattern. Ruching, pleating, cinched or tied waists, and sheer-layered looks are some common patterns. Besides, they are exquisitely cut and may have well-defined neck lines. This is probably the reason, why you cannot wear them to office everyday.
You can find classic ones in numerous designs, fabrics, and patterns. The price range also varies to a great extent to suit the budget of each buyer. You can also find a special variety of the same for juniors, here on the Internet.
Alternatively, you can also find them in your nearest designer store. But then, prepare to shell a little extra price at such high profile shops. The usual shopping malls also stock these types, but you probably wouldn't find much of variety there.
The aforementioned ideas when considered, might prove useful to select the perfect one for yourself and wear it at the right places. Furthermore, these tops can indeed make you look chic and elegant. However, choose your top wisely and make sure it doesn't look too overpowering for the occasion.