If a person calls someone" miss" it's normally because they are addressing a young woman whose name they don't know. As Daniel said it is also used when addressing someone who is unmarried.Mrs would be used for a married woman and Ms is usually used for someone who is divorced or separated Some older women who haven't been married will sometimes also use Ms rather than Miss so people don't think they have been "left on the shelf" ie. not found a husband.

In the US, if someone addresses you just as "Miss", it would be when they don't know your name and you are a relatively young woman. It can be when they want to get your attention. If they called you, "Miss (your last name)" that would be a formal way to refer to you. We use "Mrs. (Last name)" to refer to a married woman who uses her husband's last name, again in a somewhat formal context. You would never use "Mrs." (Pronounced as "missus") by itself. More and more, all women older than 14 or so, regardless of marital status, are called "Ms." This is pronounced as "mizz" and again is never used alone without a last name.

It means they a) are trying to be polite and respectful, b) guess that you are not married, c) are not sure whether you prefer to be called "Miss" or "Ms." and d) are picking the safest choice. Traditionally--before 1960, let's say--in the United States--we used "Mrs." for a married woman and "Miss" for an unmarried woman. By accepted convention at the time, if you weren't sure if a woman was married--you could usually tell by looking for a wedding ring--"Miss" was considered to be a compliment, meaning "you look young and attractive." In the 1970s, feminists argued--ABSOLUTELY CORRECTLY, in my opinion--that it was sexist to treat men and women differently, labeling women but not men according to their marital status. It was proposed that "Ms." be used as an honorific for both single and married women. The abbreviation was publicized by Gloria Steinem, particularly in the title of a magazine, "Ms." Today, in the United States, the rule of etiquette is simple--use whichever honorific the woman prefers. The problem is that one doesn't always know! "Miss" is annoying to a woman who wishes to be called "Ms." and "Ms." is annoying to a woman who wishes to be called "Miss."

Miss is not married Ms is married :)

I don't think everyone will tell you this if you are in terrible Asian country without law.