POAS stands for "Profit on Ad Spend"
We use the term POAS to emphasize the difference from revenue-based ROAS.
Fun fact about POAS - Profit on ad spend
In fact, POAS can be seen as the "original ROAS", as it is originally an abbreviation for "Return on Ad Spend" - Return being profit.
However, since the necessary profit data has not been available to platforms like Google and Facebook before we made the ProfitMetrics platform and algorhitm, it was silently accepted that the ROAS target was based on revenue in stead of return/profit.
It's the difference between focussing on top- and buttom line, which are in fact not really comparable. The latter being the absolut measure of business health, whereas the former is better considered a growth metric e.g. increased marketshare.