"[var]" refers to the value at address "var".
section .data
var dd 42
array dd 10, 20, 30, 40
section .text
mov eax, [var] ; 42 in eax
mov eax, var ; 0x8049123 (or so) in eax
mov eax, array ; address
mov ebx, 2 ; element to get (counting from 0)
mov eax, [eax + ebx * 4] ; 30 in eax
Something like that...
Best,
Frank