The Afghanistan flag that you see today was adopted in 2004.
The flag consists has a black vertical stripe, red vertical stripe and a green vertical stripe with the emblem of Afghanistan in the center of the flag over the red color.
The flag during the Taliban era had a horizontal black, white and green stripe with the same emblem. It is said that the country is the only one in the world that has had so many changes to its flag in history. The flag used today was flown for the first time at the inauguration of President Karzai.
The meaning of the flag is defined by its colors. The green means that the country has achieved independence. The red represents the fight the country had for independence and the black stands for when the country was not independence and was occupied. It is also said that the colors of the flag could mean something a little different. The black may have meant sovereign, the red modernity and progress, and green means Islam. The Shahada text on the flag means approval or testimony in Arabic.
The writing at the top of the emblem or coat of arms as displayed says, "There is no God but Allah and Muhammad is his messenger." Starting back in 1747 until present day, the flag has changed significantly.
The flag colors were black and white, solid black with an emblem, green, red and black with a black, white and yellow emblem and green, black and red with a white emblem in the upper left hand corner. Other variations were red with a gold emblem in the upper left hand corner and other variations of the same suit colors we see today.
The Afghanistan flag is displayed around the country and has been flown ever since the overthrowing of the Taliban.