I have a general idea of how the processor handles instructions but spend my time working in mostly high level languages. Maybe somebody who works closer to the iron can provide some valuable insight.

Assuming that programming languages are basically very high level abstractions of a processor's instruction set, what is the most basic set of instructions necessary to create a turing complete machine?

Note: I don't know anything about the diversity of hardware architectures but -- for the sake of simplicity -- lets assume it's a typical processor with an ALU (if necessary) and instruction stack.*

It turns out you only need one instruction to build a machine capable of Turing-computation. This class of machines that have only one instruction and are Turing-complete is called One Instruction Set Computers or also somewhat jokingly Ultimate RISC.