Army

"A.R.M.Y" stands for "Adorable Representative M.C. for Youth" and it carries quite some meaning behind it, given that "Army" is associated with the military, body armor, and how those two things are always together, the fandom name basically means that fans will always be together with BTS. BTS and A.R.M.Y have almost mirrored mages of each other and they have a relationship that is affected by each other. The symbol of A.R.M.Y is expressed as a door on their viewpoint who is waiting & welcoming BTS on the opposite door when BTS opens a new door.

About BTS

BTS, also known as the Bangtan Boys, is a seven-member South Korean boy band that began formation in 2010 and debuted in 2013 under Big Hit Entertainment. The septet—composed of Jin, Suga, J-Hope, RM, Jimin, V, and Jungkook—co-writes and co-produces much of their own output. Originally a hip-hop group, their musical style has evolved to include a wide range of genres. Their lyrics, often focused on personal and social commentary, touch on the themes of mental health, troubles of school-age youth, loss, the journey towards loving oneself, and individualism. Their work features references to literature and psychological concepts and includes an alternative universe storyline. The group has released several albums and performed on several world tours.

More Info: en.wikipedia.org