Bollinger Bands wrap a moving average in two standard-deviation rails. The squeeze, the bounce and the walk are the three readings that matter.
Bollinger Bands wrap a moving average in two outer rails set a fixed number of standard deviations away — conventionally a 20-period average with the bands at two standard deviations. Because standard deviation is a measure of dispersion, the rails widen when the stock becomes volatile and contract when it settles. The bands are a volatility instrument first and a price instrument second.

When the bands draw tight the stock has gone quiet, and quiet periods do not last. The squeeze does not tell you which way the resolution goes — only that one is coming. It pairs naturally with a symmetrical triangle, which is the same condition expressed as a shape, and it is the basis of our TTM squeeze scan.

In a range-bound stock price tends to revert toward the middle band after tagging an outer one, which is the classic mean-reversion read.

This is the misreading that costs money. Touching the upper band is not an overbought signal. In a genuine trend price will ride the upper band for days — the walk — and each touch looks like a shorting opportunity right up until it isn’t.
The bands describe where price is relative to its own recent behaviour, and nothing more. On a penny stock mid-catalyst that baseline resets so fast the reading is close to meaningless: a stock up 300% in a session is far outside its upper band and can stay there. Establish whether the stock is ranging or trending before you act on any band signal.
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