Hit Points and Hit Dice

Your character's hit points define how tough your character is in combat and other dangerous situations. Your hit points are determined by your Hit Dice.   At 1st level, your character has 1 Hit Die, and the die type is determined by your class. You start with hit points equal to the highest roll of that die, as indicated in your class description. (You also add your Constitution modifier, which you'll determine during character creation). This is also your hit point maximum.   When rolling for hit points upon gaining a level, if you roll below the average result for your hit die, you may take the average instead.

Class	Hit Die	Average
Barbarian	d12	7
Bard	d8	5
Cleric	d8	5
Druid	d8	5
Fighter	d10	6
Monk	d8	5
Paladin	d10	6
Ranger	d10	6
Rogue	d8	5
Sorcerer	d6	4
Warlock	d8	5
Wizard	d6	4

Player's Handbook, Chaper 3