In this document, anything within [brackets] is shorthand for "the value of the RAM at the location of the value inside the brackets". For example, SP means stack pointer, but [SP] means the value of the RAM at the location the stack pointer is pointing at.
Whenever the CPU needs to read a word, it reads [PC], then increases PC by one. Shorthand for this is [PC++]. In some cases, the CPU will modify a value before reading it, in this case the shorthand is [++PC].
For stability and to reduce bugs, it's strongly suggested all multi-word operations use little endian in all DCPU-16 programs, wherever possible.