Implicit learning is the knowledge that is acquired without ones awareness. The knowledge thus learnt was found to be having profound impact on the decision making/planning. There has been a constant shifting between an empiricist (learning from experiences) view and a nativist (everything is innate) view. One's failure was assumed as others success. Empiricists were constantly questioned to design a theoretical framework of knowledge acquisition. Every failure in doing so has been simply assumed as a Nativist's success. There have been a series of advancements (discussed in Reber, 1993) that have led to an increased nativist approach.
In the evolution theory, consciousness arrived later into the human system. They built upon the primitive infrastructure which runs independent of our awareness. This primitive structure is found to be more resilient and robust to mental disorders (like Amnesia, Alzheimer's etc.) as found out in several experiments on mentally challenged people.
It comes as no surprise when someone says humans rely more on implicit knowledge rather than on conscious knowledge. Almost every activity we might think of has a lot of mental processing which we aren't aware of. For example when you are asked a question like, "Why have you chosen this path over the others?", you might come up with some reason like "it's shortest/simplest etc.". The reasons rather sound like "justifications" to your act. In another instance brought up in the discussion, in the book "BLINK, The power of thinking without thinking" by Malcolm Gladwell, he talks about a Tennis coach who teaches forehand stroke different from the way he actually implements it. He consciously thinks he is doing something, he actually does something else. Though it seems hard to believe, humans don't even think rationally many a times. As Reber puts it, humans generally incorporate some "non-optimal" heuristics in decision making.
When it comes to expertise, it's about doing some task exceptionally. When we look at some expert solving a Rubik's cube, he seems to be doing it without actually paying much attention to it. This can be attributed to well-formed mental representations in his mind and improved heuristics which lead to better planning. Since there have been proofs that he doesn't perform any better than a newbie speed wise/memory wise and the fact that their expertise is limited to particular tasks, it seems legit to relate expertise with experience. As we have already talked about the primitive infrastructure that uses such heuristics for decision making, expertise can be seen as a shift from "conscious doing" to "implicit decision making".
REFERENCES:
[1] Arthur Reber's book "Implicit Learning and Tacit Knowledge"
[2] MITECS article on expertise by Anders Ericsson.
[3] "BLINK, The power of Thinking without thinking", by Malcolm Gladwell