Every indicator is price, reshaped

Take a chart. Now take the last 14 closing prices and do some arithmetic on them. The number you get is an indicator value. Do that for every bar on the chart and connect the results, and you have an indicator line.

That is all of it. RSI is a ratio of average gains to average losses over a period. A moving average is the mean of recent closes. ATR is the average size of recent bars. Bollinger Bands are a moving average plus and minus a couple of standard deviations. Different arithmetic, same input: price, and sometimes volume.

Three things follow from that, and they matter

An indicator cannot tell you anything price does not already know. It is derived from price, not a second opinion on it. If the indicator looks bullish, it is because price did something bullish recently — you are looking at that fact in a different shape.
Every indicator lags. It needs past bars to do its arithmetic, so its turns happen at or after the turns in price. Lag is not a flaw you can optimise away; it is the price of smoothing.
Nothing here predicts. An indicator describes what has already happened, more legibly. Traders who expect forecasts from it end up disappointed and then blame the indicator.

So why use them at all

Because raw price is noisy, and your eye is not a consistent measurement tool. An indicator does three genuinely useful things: it smooths noise so a trend is easier to see, it standardises a condition so you can compare it across markets and weeks, and it quantifies something you would otherwise guess at — how volatile is this, how strong was that move, how far has price stretched.

Those are real benefits. They are just not the benefit most beginners are hoping for, which is a signal that tells them what happens next.

The mistake this lesson exists to prevent

Beginners add an indicator, see a line cross another line, and treat that as a trade. The crossover is real, but it is an arithmetic consequence of recent price — it is not evidence about tomorrow. Indicators are best used to describe the current state of a market (trending or ranging, calm or volatile, extended or not) so that the decisions you make about direction, size and stops are made with better information.

How to check this yourself

Open any chart on a daily time frame and add a 50-period simple moving average. Now scroll back and find two stretches: one where price trended cleanly for weeks, and one where it chopped sideways. Watch where the moving average sits relative to price in each. In the trend it tracks price like a rail; in the chop it gets crossed repeatedly and tells you nothing. That difference is the whole lesson — indicators describe the state, and their usefulness depends on the state.