The most common actions that a monster will take in combat are melee and ranged attacks. These can be spell attacks or weapon attacks, where the “weapon” might be a manufactured item or a natural weapon, such as a claw or tail spike. For more information on different kinds of attacks, see the Player’s Handbook.
Creature vs. Target. The target of a melee or ranged attack is usually either one creature or one target, the difference being that a “target” can be a creature or an object.
Hit. Any damage dealt or other effects that occur as a result of an attack hitting a target are described after the "Hit" notation. You have the option of taking average damage or rolling the damage; for this reason, both the average damage and the die expression are presented.
Miss. If an attack has an effect that occurs on a miss, that information is presented after the "Miss:" notation.