Hit Points
Source Player Core pg. 402
All creatures and objects have Hit Points (HP). Your maximum Hit Point value represents your health, wherewithal, and heroic drive when you're in good health and rested. Your maximum Hit Points include the Hit Points you gain at 1st level from your ancestry and class, those you gain at higher levels from your class, and any you gain from other sources (like the Toughness general feat). When you take damage, you reduce your current Hit Points by a number equal to the damage dealt.
Some spells, items, and other effects, as well as simply resting, can heal creatures. When you're healed, you regain Hit Points equal to the amount healed, up to your maximum Hit Points.
Some spells, items, and other effects, as well as simply resting, can heal creatures. When you're healed, you regain Hit Points equal to the amount healed, up to your maximum Hit Points.
Temporary Hit Points
Source Player Core pg. 402
Some spells or abilities give you temporary Hit Points. Track these separately from your current and maximum Hit Points; when you take damage, reduce your temporary Hit Points first. Most temporary Hit Points last for a limited duration. You can't regain lost temporary Hit Points through healing, but you can gain more via other abilities. You can have temporary Hit Points from only one source at a time. If you gain temporary Hit Points when you already have some, choose whether to keep the amount you already have and their corresponding duration or to gain the new temporary Hit Points and their duration.
Fast Healing and Regeneration
Source Player Core pg. 402
A creature with fast healing or regeneration regains the listed amount of Hit Points each round at the beginning of its turn. A creature with regeneration has additional benefits. Its dying condition can't increase to a value that would kill it (this stops most creatures from going beyond dying 3) as long as its regeneration is active. If it takes damage of a type listed in the regeneration entry, its regeneration deactivates until the end of its next turn.
Items and Hit Points
Source Player Core pg. 402
Items have Hit Points like creatures, but the rules for damaging them are different, as explained on Item Damage. An item has a Hardness statistic that reduces damage the item takes by that amount. The item then takes any damage left over. If an item is reduced to 0 HP, it's destroyed. An item also has a Broken Threshold. If its Hit Points are reduced to this amount or lower, it's broken, meaning it can't be used for its normal function and it doesn't grant bonuses. You usually can't attack an attended object (one on a creature's person).