|This article may or may not be a stub, but it's definitely missing something.|
Specifically: Details from other games.
You can help the Street Fighter Wiki by giving us what we need.
Various types of projectile attacks exist in the Street Fighter series, and allow users to damage foes from a distance. Depending on the projectile itself, it can also serve many other purposes, such as controlling space and pressuring opponents. However, projectiles can be jumped over somewhat easily.
HistoryRyu and his Hadoken would go on to become a two of the series' many icons. Sagat, the final boss, was the only other fighter with a projectile, not counting Ken, who at the time was a multiplayer-exclusive palette swap of Ryu.
With the introduction of more characters into the series, several more projectile attacks appeared, and opened up more varied combo tactics as a result.
The Hadoken played a major part in the divergence of Ryu and Ken. Ryu was shown to have more proficiency in the 'Hado' principle of his style, and thus is able to use more variants of the technique, including the Shakunetsu Hadoken and the Shinku Hadoken, his first and "trademark" Super Combo.
Projectiles are slightly larger, and projectile-based Hyper Combos take on a more beam-like appearance.
With the introduction of the parry mechanic, non-projectile users gained a convenient advantage against projectiles, being able to nullify them completely as opposed to jumping or blocking (and thus taking Chip Damage).