Naruto. said:
Projectiles: Projectiles are objects which are propelled into the air. For eg: shurikens, kunais, etc. These are thrown towards the opponent. Now, projectiles move in a certain fixed direction, unless their direction is externally changed by blowing wind, water, etc. With projectiles the user gathers all their chakra into one central focus point and releases the chakra all in one burst or divided in several bursts, meaning the chakra is concentrated at one single point and thus the area of damage is short compared to streams, however due to the concentration being large, one single point when hit by a projectile faces massive damage.
Streams: A stream is a constant and well defined flow of an any material. For eg: a stream of wind. Here, you gather chakra, and then simply release it in a steady flow outwards toward your target and you maintain that steady flow until the chakra you've built up for the technique is no longer there. This means that streams have their power spread out evenly throughout the technique as opposed to several individualized burst of chakra that have their own capabilities, meaning you have to constantly focus on your chakra, however, you're free to alter the direction of your attack, since you still maintain the control over it until the amount of chakra that is built up gets exhausted.