An economic calendar lists scheduled data releases and central bank events with the time, the currency affected, the previous reading and the market’s consensus forecast. When the figure is published, the actual value appears beside them.
Markets price the consensus in advance. What moves price at the release is the gap between actual and consensus, the surprise. A strong number that matches expectations can be a non-event; a modest miss can move a pair fifty pips.
Not every release matters equally. Calendars grade events by expected impact. Interest rate decisions, inflation, employment reports and GDP sit at the top. Minor surveys rarely move the majors on their own.
Spreads widen and liquidity thins in the seconds around a high-impact release. Pending orders can fill with slippage. If you are not trading the event, many traders simply stand aside for a few minutes on either side.
Use the calendar defensively as much as offensively: check what is scheduled before you open a position, so a stop is not sitting a few pips from a number that will move the market.