Line chart

The simplest way of drawing a price series: one value per interval, marked and connected. The value is almost always the close price, though most platforms allow another to be chosen. The connecting line is a drawing convention rather than data. Nothing traded along it, and the market between two marked points went wherever it went.

What it keeps is the sequence of closes, which is the value most calculations rest on: moving averages, index levels and the daily returns behind a volatility figure are all computed from closes. What it discards is everything else in the interval, meaning the open, the high, the low, and therefore the range, the gaps between one interval and the next, and every reversal that happened inside a bar and ended where it started.

The trip follows directly from that. A quiet looking line can contain a day of violent movement, so a chart drawn this way understates how far a position would have travelled before arriving at the value shown. The same property makes it useful in the other direction: with the intrabar noise removed, long horizon structure and comparisons between instruments are far easier to read, which is why the same analyst reasonably uses a line chart for a decade and candlesticks for a session.