Fly
The fly is the half of a flag farthest from the pole, or the free outer edge. The word is also used for the flag's length, measured from the pole to the outer edge.
The fly end moves the most in the wind, so fine detail placed there is hard to see. Most designs keep their main symbol in the center or toward the hoist, where it stays readable. A swallowtail is a cut made into the fly edge.
In a ratio like 1:2, the second number is the fly, so the flag is twice as long as it is tall. You set this in the flag maker with the proportions menu. The flag proportion entry and the flag ratios guide explain the common choices.