Simplify the following text for a Grade 10 native English-speaking person.
Original: The Rainbow flag of LGBT movement is the official flag of LGBT ( Lesbian , Bisexual , Gay , Transsexual ) movement .
Simplified: The rainbow flag , sometimes pride flag , LGBT pride flag or gay pride flag , is a symbol of lesbian , gay , bisexual , and transgender ( LGBT ) pride and LGBT social movements in use since the 1970s . The colors reflect the diversity of the LGBT community , and the flag is often used as a symbol of gay pride in LGBT rights marches .