Among the various definitions of the world of League of Legends, there is such a thing as “Effective Health”.
To make it clear what this concept is, let’s consider a simple example. Let’s say your champion has 1500 health and 100 armor, which reduces physical damage by 50%. In this case, in order for the enemy to kill you with a physical attack, you will need to deal 3000 units of damage. It is the number 3000 that represents effective health.
In this case, a distinction is made between physical effective health and magical effective health. Accordingly, magical effective health is calculated in exactly the same way. Effective health is just a definition, but it is used quite often in everyday life.