Rules Index
Player Core Chapter 8: Playing The Game Damage Rolls
<< Step 2: Damage Type
Step 4: Reduce Hit Points >>

Step 3: Apply Immunities, Weaknesses, and Resistances

Source Player Core pg. 399
Defenses against certain types of damage or effects are called immunities or resistances, while vulnerabilities are called weaknesses. Apply immunities first, then weaknesses, and resistances third.
<< Step 2: Damage Type
Step 4: Reduce Hit Points >>