Aroon Up/Down is a technical indicator that was developed by J. Welles Wilder Jr. and introduced in his 1978 book "New Concepts in Technical Trading Systems". The Aroon indicator helps determine the direction of a trend in stocks, commodities and currencies.The stock market does not have just one trend; it has many trends. When you can detect the type of trend – whether it is an up or down trend - you have more trading opportunities to make money.