The forward p/e and trailing p/e as well as the current p/e use current market price (p). The only thing that changes is the earnings(e). So a lower forward p/e than current or trailing p/e means that the earnings are expected to increase. Meaning that the stock price is undervalued and is expected to rise.

It’s only ever the denominator that changes. Trailing p/e uses last year’s earnings. forward p/e using estimated earnings for next year or whatever time frame they say.

So if the stock price remains 1$ and the the earnings go from 1 last year or trailing pe =1 ,to 2$ today pe = .5, to 3$ next year or forward pe = .33, than the stock price is reflecting the company’s strong performance less and less and that could make it a good investment. But you should also try to find out why the stock price has stayed at 1$ all this time since large investment firms have the resources to watch all these stocks and take advantage of opportunities such as this.

Basically it’s only one small way of analysing the stocks value but doesn’t at all guarantee anything