Opera gloves are not necessarily meant to be worn in opera or theatre only, as many may think. Term "opera gloves" rather describes the certain length of the glove and usually that type of gloves is considered evening or going out style. So, length which comes up to mid upper arm or any length that is above the elbow - is called opera gloves. Opera or a full-length gloves goes over the elbow, usually reaching all the way to the biceps but sometimes it can be even full length of the arm, all the way up to the shoulder.
Certain events require by the special dress code to wear only opera gloves. Now, you know what leangth they mean. Also it should only be made of kid-lambskin leather. Some gala evenings, grand balls, performances and other grandious events might require that specific attire and accessory.
Styles have been changing throughout the time, but some traditions remain constant.
For example ties the debutante ball in England and modern day American debutante, all of them suppose to be wearing of above-the-elbow (or opera) white kidskin leather debutante gloves. Those Debutante Gloves has been recognized for over a century as one of the foremost symbols of upper-class femininity.
Don't hesitate and afraid to be feminine and classy. Those are the things that will never go out of style.