What do think may be the difference, if any, between an idea and a plan?

“I believe that Kasparov is much more aware of using logic in his games; he might often support his moves with more variations, but this seems to be more about actually proving his ideas. When Kasparov has an idea I think he works much harder at the board to find a way to put his logic to effective use in the form of concrete moves. He is very determined indeed to prove that he is right, and this is often the decisive force in his games.”—Jacob Aagaard, Excelling at Chess,  Chapter Two: “Real Chess Players”, p. 26, Everyman Publishers, copyright 2001, reprinted 2002

I would say that a plan is a form of idea: but specifically one involving foresight in the position. e.g "I will play a minority attack with a3, b4, b5 and bxc" is a plan (and therefore also an idea) but "My Bishop is better than his Knight" is only an idea.

A plan implies some specific process that is carried out to achieve an objective; an idea can be more abstract.

An Idea it is a Spark of Thought!

Plan is an Order and Execution of an Idea shadow of the Tally Wings!

Greg