The adjusted close, shown on the right side of the history table (if available) in yahoo finance, factors in the impact of dividend payments. This can give a more accurate view of historical performance, particularly for stocks that pay dividends regularly. It is typically only available for historical prices that go back as far as 1970, and it may be less useful for longer durations or stocks with more dividend payments along the way.
Sometimes the daily Open/Close and Adjusted Close from Yahoo (or other data sources) do not match with our first tick and intraday data. This is usually the result of transactions that occur outside the regular market session. This article explains why this happens and what to do about it. This also applies to Stock Trading Volume, although the difference is more likely to be due to different ways of measuring volume than to any differences between our data and Yahoo’s.