Memory Indirect 
  Jmp ($4000) (Mos Technology 6502)
    Jump (change PC) to memory location named in memory locations $4000
    and $4001 (little-endian)


Register Indirect 
  MOV [BX],25  (Intel 8088)
    Moves byte byte value 25 (an immediate value) to the memory location
    pointed to by BX base register.  
   
    The address is an offset from the beginning of block of code or data 
    and also uses the paired "unnamed" segment register, in this case (DS).

  MOV AX,[SI] (Intel 8088)
    Here SI is a index register added to DS segment register.  That it
    is an index and not a base is the cpu's choice. For the 8088, the base 
    and index pointers are both 16 bit.