I'll keep it simple...hope it is not too simple

The income is determined by substracting all expenses from the total revenue. If positive, then taxes are due.

The losses are cummulative and can be applied against future income.

Future income would basically be tax free until such time as accumulated losses are used. There are other variable, like capital gains, etc.

Earnings (EPS) are calculated using income divided by Number of Shares, can be positive or negative.