The letters L.G.B.T. are used to represent the all inclusive Lesbian, Gay, Bisexual, and Transgender community. Within that community there are many subsets to represent how individual people personally identify themselves. Although the word "gay" is often used to refer to the entire community, it's more appropriate to limit that word's usage when referring to gay men. It's also acceptable to use the word gay when referring to a group of gay men and lesbians, although, if you are referring to lesbians along then it's more appropriate to simply say
lesbians rather than "gay women."
Since he LGBT community includes more than just gay men and lesbians, it's more appropriate to use LGBT wherever you are not specifically referring t one subset of the community.
Other letters are routinely assigned to this acronym and include
Q frequently associated with Questioning (those who are coming to terms with their identity and not sure where they fall in those categories, if any),
I, for Intersex (which represents individuals who through chromosomal and physical characteristics, due not necessarily identify as male or female). Still other letters and terminology is used to represent others; for some individuals, the umbrella term "queer" is preferable. As ever, it is important to note identity is highly personal, and many people also avoid the use of the acronym in hopes to draw attention to the individual groups of people, rather than forcing them all together int o1 group.
We use this word a few times to refer to the typical couple that jewelers have been servicing forever. You know, the opposite-sex couples.
We might say things like "traditional customer" or "traditional couples" as a way to help you understand the difference between what was then and how it's different now.
Our goal is to completely do away with words like this. Eventually society will just refer to all couples as just couples.