Billboard Liberation Front is a group of people who want to make advertisements on big signs, also called billboards, better. You know how you see big signs while driving or walking around that have pictures and words on them telling you to buy things or go to places? Well, sometimes those signs can be annoying or make you feel bad about yourself.
The Billboard Liberation Front thinks that advertisements should be more truthful and less pushy, and they try to change certain parts of the ads to make them better. They do this by climbing up to the billboard at night when no one is around, and using special tools to change the pictures or words on the sign.
They're like superheroes who want to make the world a better place by making ads more honest and less harmful. However, it is not a legal activity and people may get into trouble if they are caught.