What exactly is a critical section?

Question

Just want a little clarity on the this. Imagine I use the windows api of EnterCriticalSection. I call all of them with EnterCriticalSection(&criticalsection);

Answer 1

Critical section is a code chunk. If any thread entered it, no other thread can enter until it's free. If 1 and 2 are different critical sections (i.e. handled by a different semaphore), someone can enter 2 if 1 is occupied.