I think I forgot to talk about Stress and Consequences, which is the equivalent of Health/HP. reference the character sheets with the boxes and this will make more sense. Also rea dmore here:
https://fate-srd.com/fate-core/conflicts
If you hit someone with an Attack, however much you beat their Defense roll by is how much damage you do.
When you take damage, you mark off Stress. Stress clears out between encounters.
By default, each character has 2 Mental and 2 physical Stress boxes.
If you have the Physique or Will skills, they add one or two more boxes depending on level.
A 1 or 2 in Physique/Will gives an additional 3pt Stress box, and a 3 or 4 in the skill gives a 4 pt.
So Tam, who has 3 Will and 2 Physique, would have 1,2,3 and 4 pt Mental Stress boxes, and 1,2, and 3pt Physical Stress boxes.
So if he took 2 pts of damage, I could check off the 2pt Stress Box. If I then took 4, i could check off the 4pt box. if I then took another 4, I would have to take a Consequence.
You can't combine boxes. So if you have the default 1 and 2 pt boxes and you take 3 damage, you can NOT check off both boxes. You have to take a Consequence. A consequence reduces the damage, and then any remaining you can use Stress for.
Every character has 3 consequence slots - Mild, Moderate, and Severe, which reduce 2, 4, and 6 damage, respectively.
Unlike Stress, Consequences do NOT go away after encounters. They are temporary aspects that can ONLY be bad. The GM can tag them to get bonuses against you. They are like any other kind of aspect, but just bad.
They go away over time, with skill rolls (Lore or Empathy for physical or mental healing), and roleplaying.)
Once all stress and consequences are filled up, the character is taken out, and the GM describes what happens. generally they are not dead, but captured, saddled with more disadvantages, etc.
PS - Jerry you can decide how much stress/consequences bad guys have. Mooks might just have a stress box or two, where villains might have higher stress boxes and all three consequence slots.
Read the book, refer to the documentation, or ask me when it comes up. But do note stress boxes on character sheets!