In a way, it's applicable to all gambling situations, although it doesn't always look exactly the same. It's basically a way to quantify risk vs. reward to determine if something is "expected" to be profitable. I mean "expected" in the mathematical sense of probability theory and statistical analysis.

It's basically ( total risk ) / ( total reward ) = alpha.

If alpha is less than the "win frequency" or "equity", then a gamble has a positive expectation value; it is +EV.

Spoonitnow is applying this fundamental principle to the game of poker. He understands this concept thoroughly, and I consider him an expert on the subject (for what a monkey's opinion is worth).