Health is a primary resource in Paragon. Represented as HP in game, all units, including Heroes, Minions, Neutral Monsters, etc., have health. A Creatures health can be increased by using healing abilities and items, while it can be reduced by taking damage. When a creature's health is reduced to zero, that creature dies.
Maximum Health is an attribute that affects the highest amount of health that a creature can have. With each hero level, a hero's maximum health increases along with their current health. Gems and Cards may be purchased to increase heroes' maximum health. When a hero spawns, their health is at their maximum. When a hero is shielded, they may have a health value that's higher than their maximum health since shields aren't affected by that cap.
Effective Health is a term that's not explicitly used within Paragon, but rather is a concept that is a direct consequence of combining multiple facets in the game. When damage is dealt to a creature, multiple factors determine how much health that creature loses. Other than the amount of damage itself, the biggest factor is Armor. When damage is dealt, it is reduced by a percentage based on the amount of armor that a creature possesses. That same percentage can be used to express the Effective Health that a creature has. Instead of using armor to determine how much less damage an attack does, it can rather determine how much damage a creature can take from an attack of a certain type.
For example, if a hero has 1000 health with enough ability armor to reduce ability attacks by 25%, then one may also say that that same hero has an effective health of 1250 against ability attacks. If that same hero doesn't have any basic armor, then their effective health is unchanged from their actual health.
Healing and Health Regeneration
Healing in Paragon comes in many forms - Lifesteal, Health Regeneration etc.
Anti-Heal in Paragon is called Blight. Blight reduces the effectiveness of all the healing sources listed above by 40%.
The only other note to take here is healing modifiers and Blight work exactly against each other. If someone Blights you and you have the Card Vital Waters which increases your healing by 10%, Blight would reduce your healing by only 30% as 40-10 = 30.