Formal evening wear is usually black and white clothing. Men usually wear tuxedos or a tailcoat accompanied by a tie and a vest. Women will wear dresses.
You'll have to ask your supervisor; no two internships are alike. However, technically speaking, "formal" and "semi-formal" refer to evening wear like a tuxedo or evening gown, so neither of these would be appropriate unless your internship is in an Opera house. At my internship I wear a suit and tie, or a tie and a sport coat.
Tuxedo's are formal evening wear. Most would think hiring a morning suit more appropriate.
Most gala dinners require you to wear formal attire. This would include a suit and tie or an evening gown. You would also want to wear fashionable jewelry and shoes to such an affair.
Black Tie. This means as close to formal as possible. Your best evening gown, if its a female, suit for the man.
You could wear a dark blue or black suit to a 5pm wedding. You could also just wear nice pants with a collar shirt.
A semi-formal event is one in which the expected dress attire is moderately formal. Dresses or pant suits for women are appropriate. Men can get away with a coat and tie before 6 p.m. and a dark suit after 6 p.m.
If there is a receiption afterwards, the ceremoney if semi-formal. Man /suit and woman cocktail dress, dinner or evening dress.
Butlers typically wear formal attire called a butler's suit, which consists of a black tailcoat, matching trousers, a white formal shirt, a black waistcoat, a white bow tie, black formal shoes, and white gloves. The attire is often completed with a name tag or a lapel pin identifying their role.
A "formal" party or "semi-formal" party are two terms used. Formal usually means a long evening gown for women and a tuxedo for men. Slightly more formal is called "White Tie" and semi-formal usually means a dress suit or tuxedo for men and a shorter knee-length party dress for women.
No, you may not wear a dark blue shirt and black slacks to a black-tie optional event. Even though the black tie is "optional", it still indicates that guests should wear very formal clothing. It is likely that many of the guests will be wearing tuxedos, but a dark colored suit preferably black) with a crisp white shirt and a darker tie are still appropriate. At the bare minimum, you might be able to blend in without the jacket, but it is best to wear the full suit. Ultra formal events, which are rare in America, are "white tie formal". This includes things like the Inaugural ball for the President. Just below this is "black tie formal", which includes things like the Oscars. "Black tie optional" is just below this distinction, so these events are still considered very formal. Hence, the need for the dark suit if one cannot wear the tuxedo. For more information see this wiki post: http://wiki.answers.com/Q/What_does_Black_attire_mean
Macy's carries a large array of evening wear for both men and women. Men can find both classic suit and tie ensembles as well as less formal attire. Women will have an endless selection of designer dresses.
Silverware.