A 52-week high is the highest price a share has traded at over the preceding 52 weeks (one year); a 52-week low is the lowest. Both are simply the maximum and minimum of the price series over a rolling one-year window — as each new trading day is added, the window's oldest day drops off, so the specific high or low being reported can change as older extreme values roll out of range even without any new extreme being set.

These figures are purely descriptive of where a share has traded recently relative to its own history — they say nothing on their own about why the price reached that level, or what has happened to the underlying business since. A share can sit at its 52-week high after a long, gradual rise or after a single sharp jump on a specific piece of news; the 52-week high figure alone doesn't distinguish between the two. The same applies at the low end.

Trading volume — the number of shares that changed hands in a session — is a separate figure often read alongside price extremes. Rising volume alongside a price move (in either direction) is commonly read as showing the move involved a relatively large amount of participation from the market, compared with the same size of price move occurring on unusually low volume, where fewer shares changed hands to produce it. Volume by itself doesn't indicate direction; it describes how much trading activity accompanied whatever price movement already happened.

On this app, a company's period high and low (shown alongside its price chart) are calculated over whatever date range is currently selected — 1 month, 6 months, 1 year, 5 years, or the full history available — rather than being fixed at exactly 52 weeks, so the same company can show a different "period high" depending on which range is selected. The specific 52-week convention described here corresponds to the 1-year range.