Attacking

When you make an attack, choose a valid target and make an attack roll. If the result of the roll equals or exceeds the target's AC, the attack hits; otherwise, the attack misses. If the effect letting you attack doesn't specify a means of doing so, you can use any weapon you're wielding.
Every attack is either a melee attack or a ranged attack. Melee and ranged attacks follow different rules, described below. Every attack is also either a weapon attack or a spell attack.

Attack Roll

An attack roll is a d20 plus whatever bonuses apply, such as an ability score or your proficiency bonus. You have disadvantage on an attack roll against a target that you can't see.

AC

AC, short for "armor class," is a number that determines how hard you are to hit. Unless otherwise specified, your base AC equals 10 + your Dexterity score, and your total AC is your base AC plus other modifiers. Many creatures have armor that changes their base AC.

Melee Attacks

When you make a melee attack, you must choose a target within a specified distance. For melee weapon attacks, this distance is the weapon's reach.

Ranged Attacks

When you make a ranged attack, you must choose a target within the attack's range. Making a ranged attack also provokes opportunity attacks unless you make the attack hastily, which causes the attack roll to have disadvantage.

Range

A ranged attacks' range determines how far away the target can be.

Long Range

Some ranged attacks have a long range in addition to their normal range. The target can be as far away as the long range, but you have disadvantage on the attack roll if the target is beyond the attack's normal range.

Weapon Attacks

Weapon attacks require the use of a weapon, such a sword, bow, or fist.

Reach

Every melee weapon has a reach, which is 5 feet unless otherwise specifed. A target must be within a melee weapon's reach in order to attack it with that weapon.

Weapon Attack Roll

When you make a weapon attack, add the following to the attack roll:

Weapon Damage Roll

When you hit with a weapon attack and the weapon deals damage, add the following to the damage roll:

Spell Attacks

Spell attacks require the use of a spell or other magical effect. The source of the spell attack specifies what you add to the attack and damage rolls.