In The Matrix, Neo is offered a choice between a red and a blue pill in an iconic moment.
The blue pill would take Neo back to his normal life, and the red pill would show him how deep the rabbit hole goes (IE: Wake him up from the Matrix and show him the real world with all the humans in their storage pods.)
However, what pills was Morpheus actually giving him, and how would the red one get him conscious? Was it just a sleeping pill, then Morpheus' crew did the work? What were they?
"You take the blue pill, the story ends. You wake up in your bed and believe whatever you want to believe. You take the red pill, you stay in Wonderland, and I show you how deep the rabbit hole goes."
Morpheus to Neo...
So, Morpheus offered Neo two totally different kind of pills, one being the epitome of illusional ignorance and other being the paragon of enlightenment.
Also, about the Red pill
MORPHEUS: The pill you took is part of a trace program. It's designed to disrupt your input/output carrier signal so we can pinpoint your location.
The pill helps the crew locate a person.
How?
The pill is actually a tracing program that disrupts the carrier signal of the pod-human's mind, making it possible for a hovercraft operator to locate the pod that holds the human, and sending commands that force it to go offline and awaken its inhabitant.
Now, the Bluepill
If the human chooses to continue their life within the Matrix, the virtual blue pill presumably contains a reset command that sends the person back to a previous state to continue their existence within the Matrix, and completely forget anything about the conversation. That isn't necessarily to say that the decision is permanent as redpills are always willing to help out anyone who is ready to leave.
some more source to read: http://www.dailyscript.com/scripts/the_matrix.pdf
