The pill analogy in the matrix and here refers to the choice between living in blissful ignorance (blue pill) and embracing the somewhat painful truth of reality (red pill).
It's context on SS and other PUA sites is the reality of what women are capable of doing and what their actions often entail, that their ***** is not on a pedestal and that you are the prize to be won, not they. That you are essentially above them despite feminist claims, and not for any natural-social order, but for the simple fact that they WANT you to be that way, they desire it, and much more than AFC chumpery submitting to their will.
That's the best I can summarize it. It includes all the truths about how often they will flake, ****-test you, and ultimately act in total self-interest if they feel they don't have to work for your affection.
All these ideas are subject to variation and circumstance, but it seems to be the general rule for any type of desirable woman.
edit: You could also say the red pill includes understanding behaviors about yourself that are limiting and what is required to change them.
