The other day, I was in M&S near where I live, and wanted to buy a couple of shirts with a collar fitted with buttons (to fasten the sides of the collar to the shirt, at the front). As far as I know, such collars are called button-down collars. The shop assistant said that this type of collar is called an Oxford collar. I have done a search on line and what I have found does not quite confirm this assertion. I am just curious to know whether Oxford collar is used to describe a certain type of shirt and, if so, which one, and whether Oxford shirt is used. I am not familiar with these terms. Thanks.