Can you help with assembler?

Question

assembler

Explain the command MOV ES, 87h
Difference between MOV AX, SI and MOV AX, [SI]

Answer 1

MOV ES, 87h

int es = 0x87

MOV AX, SI

int si = ...;
int ax = si;

MOV AX, [SI]

int * si = ...;
int ax = *si;

Answer 2

There is a conditionally array (memory) of 3 elements [100, 200, 300]
SI = 1
MOV AX, SI- assign a value - AX = SI = 1
MOV AX, [SI]- assign a value from memory AX = [SI] = [1] = 200