Small bars (or bodies as they are technically called) are a sign the market maybe consolidating its position or thinking about its next move. Long bodies could indicate the market is again on the move and looking to test new levels. Some charting packages will only show the close on the bar, many traders elect to use this style with great success. Some say the opening price does not give a true indication of market sentiment and choose to ignore it. There is a marked difference when drawing trend lines on a line chart compared to a bar chart. With a bar chart you get the entire trading range and a trend line can be drawn using these ranges as opposed to only using closing price data on a line chart.

Candle stick Charts
Reading Candle stick charts
Candle stick charting was developed by the Japanese several centuries ago and has undergone resurgence in popularity in recent times. This form of chart is by far my personal favorite and I usually use it exclusively. Although more complex to understand, once mastered, candle charts can give you the best overall view of market sentiment.