In order to understand LGBT, we have to understand the two terms—Sexual orientation and gender identity.
Sexual orientation refers to the physical attraction you feel towards a man or a woman. As you know, the general sexual orientation is that a person should be attracted to the opposite sex (heterosexual).
Gender identity refers to the physical attributes of a person. The greatest identity is the genitals of a person that could prove they are male or female gender.
Then what is an LGBT?
L means Lesbian. A lesbian is a woman in gender but is sexually attracted to woman. We call a woman like this homosexual woman.
G stands for Gay. This refers to a man in gender but is sexually attracted to a man. We call this person a homosexual man.
B stands for Bisexual. These are people who can be sexually attracted to both sexes. They can still go with the normal (heterosexual) relationship that is accepted in the society.
Note that LGB are people whose feeling varies over period of time. In other words, the feeling they have is not in-born and that they will just feel they are different when they begin crushes at the age of 10 or eleven. But this is not always the case.
T refers to Transgender. Who are they? A trans woman is a boy by genitals but thinks and acts as a woman. A trans man is a woman by genitals but thinks and acts as a man. These people have a problem in how they were created. Biologist say that these problem is caused by hormonal imbalance such as having an XXY or XYY chromosome instead of having an XY or XX chromosome.