Here is teardown of 10 A DIN rail mounted miniature circuit breaker (Biltema brand)
What you see when you open the case
Turn around – circuit open/off/tripped
Device reseted to “on” position
On the left side of mechanism there is bimetallic overcurrent triggering mechanism – load current goes through bimetallic strip and heats it.
On the center there is solenoid coil for quick tripping on short circuit.
Contacts that make and break the current are on right. On bottom there are stack of metal plates that take part in breaking the high short circuit current quickly.
Related posting with more background information: