Weapon attack stats
http://wiki.guildwars2.com/wiki/Hunter%27s_Shot
the skill you mentioned seems pretty straight forward. its one shot that does damage and inflicts vulnerability on the target. at the same time your pet gains swiftness. if your projectile goes through the appropriate combo field it will trigger a projectile combo finisher.
the explanation clarity are really on an ability to ability basis. for example: http://wiki.guildwars2.com/wiki/Chaos_Storm. the skill states “applies random conditions to foes and random boons to allies” and simply has a list of of boons and conditions
the first line of the skill generally explains how the rest of the skill description should be interpretted