This tool uses game theory to compute the optimum bluffing frequency against a single opponent. It assumes you know that your opponent has a good, but not great hand, and will either call or fold. Given the pot size and how often you would have a winning versus losing hand in this position, it computes the bluffing frequency. It is optimal in the sense that your opponent can gain no advantage by folding more or less often.
The tool also generates a random number, compares it with the bluffing frequency, and suggests a course of action.