When evaluating a stock one should look at not only earnings but how those earnings are growing. The rate of growth helps to determine where the earnings will be next quarter, next year, or five years down the road. If you see a stock with a P/E (Price/Earnings) of 100 that is usually do to a high growth rate. The investers a paying a large premium for the company today due to the expected growth of the earnings for the company in the future. This type of investing tends to be more risky due to the fact that the company may fail to meet expected growth rates. On the other hand these stocks can exceed expected growth rates and reward investers who took a chance on them with stellar returns. Growth rates can also be used too compare one company to its peers. Companies in the same industy should have similar growth rates. Differences in these rates may indicate problems within a specific company.
Price to earnings of 100 are quite impossible and if they appear it is best to avoid the stock since you will inevitably lose money.