Relative Strength, Comparative (RSC) compares the price movement of a stock with an index, a sector or another stock to illustrate how they are performing relative to one another. It is derived by dividing one security's price by a second (or "base") security's price. The result of this division is the ratio or relationship between the two securities.

When the indicator is moving up, the security is out-performing the base security. Sideways movement means the stock and security are rising and falling by the same percentage. When it is moving down, the security is performing worse than the base security. 

Use the indicator to to compare a security's performance with a market index or to develop spreads - buy the best performer and short the weaker one.