A magic weapon adds an enhancement bonus to attack rolls and damage rolls, so a +3 flameburst longbow adds +3 to all attack rolls and damage rolls made with the bow. This bonus does not apply to any ongoing damage or other damage that might be applied to the attack. If you’re not proficient with the weapon type, you don’t gain the proficiency bonus to attack rolls, but you still gain the enhancement bonus of the magic weapon.
The category determines what kind of weapons can be enchanted with that particular set of qualities. “Any ranged” includes projectile weapons and weapons with the heavy thrown or the light thrown property. “Any” or “Any melee” includes all applicable categories.
Ammunition: Ranged weapons such as bows, crossbows, and slings impart their magic to appropriate ammunition fired from them. Ammunition (such as arrows, bolts, or sling stones) doesn’t come in magical versions. You can’t craft (or find) a +1 flameburst arrow or a +3 sling stone.
Thrown Weapons: Any magic light thrown or heavy thrown weapon, from the lowly +1 shuriken to a +6 perfect hunter’s spear, automatically returns to its wielder’s hand after a ranged attack with the weapon is resolved.
Catching a returning thrown weapon is a free action; if you do not wish (or are unable) to catch the weapon, it falls at your feet in your space.