There are two versions. Trailing P/E uses the profit already earned; forward P/E uses next year's forecast. Forward is usually lower, because forecasts assume growth.
A number in isolation is useless. Compare it with the company's own five-year average, with direct competitors, and with the wider market.
The most useful reframing: a P/E of 40 says the market expects profits to grow substantially. Your job isn't to judge the number — it's to judge whether that expectation is reasonable.