Price of an instrument is either in a trending phase or in a consolidation period. During strong trend periods prices move uninterrupted from one price level to another. During consolidations prices move in both directions without producing any meaningful or sustained price change and will form well-defined support and resistance areas on the charts. A support range represents a concentration of demand, and a resistance range represents a concentration of supply.
A resistance level is an approximate level or fairly well-defined price range, where previously advancing price action meets resistance in the form of strong selling. A support level is an approximate level or price range where a preceding decline meets support, in the form of strong buying. A possible explanation for appearance of such well-defined price boundaries in the form of support and resistance can be the fact that the public tend to remember previous levels the price has traded.