Volume Weighted Average Price. This exactly what the name implies. VWAP starts fresh every morning at the open and starts to calculate as the day goes on and can be printed on a chart as the day progresses.
The VWAP line can be an excellent setup for daytrades. Strong stocks that are making new two day highs are often buys when price pulls back to the VWAP line. Conversely, weak stocks making new two day lows are often shorts when they rise to the VWAP line.
The VWAP is most effective when charted on trading hours only and ShadowTrader is partial to the five minute chart although in theory the VWAP line should be the same no matter what timeframe chart you are on. It is common for there to be a slight discrepancy in the VWAP calculation between various charting platforms.