dow theory is the first ever attempt made to understand and follow the market by following the supply and demand. it is represented by a line chart and requires minimum of 2years prior data, the line chart is classified into tops and bottoms and further classified into higher tops, higher bottoms and lower tops, lower bottoms. even though it only shows the direction it does not show the price behaviour. but it stays on top because it is used as the base from which all other theories were based on. the support and resistance represent the key points in which demand and supply meet.