Hit Points are how much damage you can sustain before you are incapacitated or die in the game.
At 1st level, your character has 1 Hit Die, and the die type is determined by your class.
Formula to calculate hit points 5e.
At first level, you calculate your hit points by adding your constitution modifier to the highest possible total of your class’s assigned hit die.
Your hit point maximum is the amount of hit points you have at full health and change as you take damage.
Your Constitution modifier contributes to your Hit Points.
Suppose your hit dice at the wizard class is +6 in the 1st level, calculate your hit points if your constitution modifier is 4.
Therefore, the hit points are 10.