An arrow can be a :

Directional Indicator

An arrow can be an image or dynamically drawn shape that indicates a direction or course of action to the player. An arrow can also be used to point out a location to the player.

A "Go Arrow" is almost unique to fighting games. It's sole purpose is to tell the player that all the enemies in that "zone" have been defeated and therefore the player can move forward. Go Arrows commonly look like, well, arrows, or a finger pointing with the word "Go!".

Drawing Arrows

There are many ways to draw arrows.

Arrow as a Projectile

An arrow can be a projectile that looks like an arrow (as in bow and arrow). In general terms an arrow projectile is classified as a bullet because the arrow is "dumb" (doesn't follow anything) and it continues on a straight line once shot.

The amount of arrows in this case is ammo.