Recovery and regeneration

Here is what restores you.

Life. Baseline life regeneration in combat is zero. You recover through:

Flasks (The flask belt).
Leech: a percentage of damage you deal returns instantly, up to 20% of your maximum per second.
Life on hit and life on block.
Healing spells such as Magic Patch and Intense Healing (Spells by vocation).
Regeneration from gear, runes, the tree and passives.
Energy shield recharge, a separate pool (Energy shield).

Mana. Baseline mana regeneration is a small percentage of your maximum every second, scaled by items and the tree. Mana flasks refill mana (The flask belt).

Resting. If nothing has damaged you for about six seconds, both life and mana refill over roughly twenty seconds, even without food. In a hub you are fully healed at once (Hubs and waypoints).

Life recovery is a stat: "% increased life recovery" scales every life you gain, including flasks and leech. Some keystones and map modifiers halve it or cut it (Keystones, Map modifiers).

Blood Magic makes spells cost life, not mana. Crimson Pact doubles leech but removes regeneration (Keystones).

Defence is recovery. Avoiding damage with armour, block, evasion and energy shield beats healing it. Pick the mixture that suits your build (The three defences).

Where it applies. Leech happens after a hit lands. Flasks heal over about four seconds.

On death. Life and mana are restored in the temple (The death rule).