Gap shooting / aiming
Aiming is a bit similar to how you aim with a rifle.
1) You draw the string, anchor in your anchor point, which must be on the face. Close one eye and look by second eye forward to arrowhead and on. It is not (resp. doest not have to be) along the line of arrow! It is the line from your eye, through the arrowhead and forward.
2) You turn with the bow, so that the line you watch goes exactly to the center of target.
3) That's not enough! The arrow after release may, or may not, fly over the line you watch. Depending on the bow construction, arrow flexibility and your anchor point the trajectory of arrow may bias. When choosing bow and arrows you chose it so that the bias will be small , but you always have to consider that there will be some. OK; you know your bow and arrows because you shot it many times, and you know how large the bias will be and in which direction. So you the turn with the bow so that you line ends a bit to the side from the target center, in order to compensate the bias for the distance.
4) That's still not enough! The arrow, on contrary to the rifle bullet, loses speed quite a lot. In order to hit distant target you have to shoot in arc. That means that you have to aim higher then you want. How much? Well, you know your bow and arrows, and you have tried it before. There is a table in your head that says "in the distance of X meters you have to aim Y centimeters higher". You than adjust aiming according to this table.
5) You finally release the arrow, it flies and hits exactly bullseye.
The difference between intended target and aiming point is the "gap", that made it to the name of technique. Gap shooting is principially slow, because you have to consciously consider several factors. It is demanding for concentration and quality of motion. If you do not draw the string always exactly in the same way, your "computation tables" will not work.
On the other side the gap shooting has one big advantage - it is controlled consciously. If you miss, you know how much, and you can adjust next aiming according to it. There is a piece of mechanicity, mathemathical exactness in it, which brings reliability. You can also quickly consciously adapt to a different bow or arrow - with several first shots you find how much they bias, and take it in account during nech aiming.
But in my oppinion it is boring :-)