After acquiring the Graziano turquoise bead necklace with help from Marianna, I dashed to the YLF store to refresh my memory on what Angie had said about it. A sentence in her description revived a few questions I've been wanting to sort out about tops. Here was the sentence:

Wear this over a white knitted top, shirt or blouse
with jeans and a pair of dressy flats and you’re in business.

Could someone please explain to me the difference between a top, a shirt and a blouse? I've always been mystified at the differentiation between buttondowns and blouses, too, since the words were interchangeable in my home growing up.

Another terminology question, while I'm at it. Could someone kindly describe the silhouette of a sheath dress? I'm unable to picture this item when it's referenced. Is it a cut or style that someone of my shape could wear?

Thanks, ladies, and pardon my ignorance!