Stack(s), Registers in ActionScript ByteCode AVM2, which all are there?

Question

From the AVM2 Overview PDF I encountered references to two types of stacks - Scope Stack and Operand Stack.

1) I assume these are two different memory stacks, each handling different things. Are there even more stacks?

2) pushstring "hello" - this would push a start of memory address where "hello" string is located onto Operand Stack. Right?

3) setlocal 0 - this would store a value from the stack (above) into register0 by popping it off. Right?

4) PushScope() - hmm, docs say pop value of stack, push value onto Scope Stack. Why?

I know a little bit of NASM but ABC seems more complex than that. Especially I'm confused about Scope Stack and the whole concept of multiple stacks.