Indicator

An indicator is a calculation applied to price, volume, or both, that gets plotted on or below a chart to help a trader see something that raw price data doesn't show clearly on its own. Instead of just looking at a jagged line of prices moving up and down, a trader applies a formula to that data and gets a smoother, more interpretable output — a line, a set of bands, a histogram of bars, or something similar.

Indicators fall into two broad groups, based on where they appear on the chart. Overlays sit directly on top of the price chart, using the same price scale — a moving average is a common example, drawing a smoothed line through price to show the general direction of a trend. Oscillators sit in a separate panel below the chart, usually on their own scale, and tend to measure momentum or speed — how fast price is moving, or whether it has moved "too far too fast."

Every indicator is built from past data. It takes prices (and sometimes volume) from previous minutes, hours, or days and does some math on them — an average, a ratio, a rate of change — then plots the result. This means an indicator is, by construction, describing what already happened. Some indicators are built to react faster to recent moves (making them more sensitive but also more prone to false signals), while others smooth more heavily (making them slower but steadier).

The nuance that trips up beginners is treating an indicator as if it predicts the future rather than describes the past. An indicator can flatten out noise and highlight a pattern, but it cannot see a news event coming or guarantee price will keep doing what it's been doing. Most experienced traders use indicators as one input alongside price action, volume, and context — not as a standalone signal that tells them what to do.