What is a Doji Candlestick Pattern?

A Doji Candlestick Pattern occurs when the opening and closing prices are basically at the same price, resulting in a very small body. Remember that the length of the upper and lower wick (which replicates the intra-period values) have no effect on the closing price.
The explanation of the basic Doji is that there is no strong way for the market. This should make you suspicious till a stronger signal presents itself.