The longer Link charges his bow, the farther the arrows will fly and the more powerful they'll be. At maximum charge, they'll fly perfectly straight.
Hero's Bow is Link's Neutral B attack, in which Link will use his Hero's Bow to fire an arrow in a straight line. Link's Hero Bow was introduced in Super Smash Brothers Melee, and has remained Link's neutral B attack since, following Super Smash Brothers Brawl and Super Smash Brothers 3DS/Wii U. Link's alterations, Toon Link and Young Link, also utilize the Hero's Bow move.