Price versus time: the only two axes

Every chart you will ever look at, in any market, is the same simple object: a record of what price something traded at, plotted against when it traded. That is the whole thing. The horizontal axis is time, moving left to right. The vertical axis is price, going up as you go up. Everything else on a chart is decoration layered on top of that record.

If you finished Trading 101 you already know that "price" here means the last price at which a buyer and a seller actually agreed. A chart is a history of those agreements. It does not know why anyone bought or sold. It does not know about earnings, interest rates, or the news. It only knows that at 10:31 someone paid 101.20, and at 10:32 someone paid 101.35.

What the chart is not

New traders tend to treat a chart as a prediction machine. It is not. It is a rear-view mirror with very good resolution. Reading charts well is about understanding what already happened, what kind of traders were involved, and where they are likely to be stuck. Prediction, if it happens at all, comes from that understanding, not from a shape on the screen.

The chart also is not the market. The market is the crowd of people and machines sending orders. The chart is a shadow that crowd casts. When you learn to read it, you are learning to reason about the crowd from its shadow.

The simplest chart

Here is the whole idea in ASCII. Each dot is a trade; time runs left to right.

price
 104 |                         .
 103 |                    .  .   .
 102 |          .   .  .            .
 101 |   .  .     .                    .
 100 | .                                  .
     +----------------------------------------> time
      9:30      10:00       10:30       11:00

You can already say things about this. Price went up for an hour and then came back down. Whoever bought near 104 is now losing. Whoever sold near 100 early on is also unhappy, because price ran away from them for a while. That is chart reading. Nothing mystical has happened.

Why price is plotted against time and not something else

Time is the one thing every trader shares. A trade at 10:31 is a fact regardless of who you are. Because of that, plotting price against time lets millions of people look at the same picture and reason about the same crowd. Some traders plot price against volume or against number of trades instead; you will meet those later. For now, time is the default and it is what almost every platform shows you when you open it.

Key idea: A chart is a history of agreed prices, plotted against time. It records what happened; it does not predict what will happen. Every skill in this course is about reasoning from that history.

Scale matters more than people think

Two details of the vertical axis change how a chart looks without changing anything about the market.

The first is the range shown. A chart that shows 99 to 105 makes a one-point move look enormous. A chart that shows 50 to 150 makes the same move look like a flat line. Before you decide a move is "big," check the axis.

The second is linear versus logarithmic scale. On a linear scale, each gridline is the same number of dollars apart. On a log scale, each gridline is the same percentage apart. For a stock that went from 10 to 200 over years, linear scale makes the early years look like nothing happened. Log scale shows the early doubling from 10 to 20 as the same vertical distance as the later doubling from 100 to 200. Most intraday charts use linear scale and it does not matter. Long-term charts usually look more honest on log.

Try it: Open any chart on your platform. Find the axis settings and switch between linear and log scale on a multi-year daily chart. Notice which moves suddenly look bigger or smaller. Then drag the vertical scale to compress and stretch it. Nothing about the market changed; only your impression did.

The one question every chart answers

When you look at a chart, the first question is always the same: over this window of time, did buyers or sellers get their way? Everything you learn in later modules is a more precise version of that question. Candles answer it for one period. Trend answers it over many periods. Levels answer where the fight was hardest. Volume answers how many people showed up to fight.

Keep that framing. A chart is a scoreboard between buyers and sellers, updated continuously. Your job as a reader is to figure out who is winning, who is trapped, and where the next fight is likely to be.

Recap

• A chart plots agreed trade prices (vertical) against time (horizontal). That is all it is.
• It records the past; it does not predict. Reading it means reasoning about the crowd that produced it.
• The vertical axis range and linear-versus-log scale change how a move looks without changing the market.
• The first question for any chart is simply: did buyers or sellers get their way over this window?