RPM (Revenue-Per-Thousand)

RPM is the acronym for Revenue Per Thousand, and refers to the average revenue generated for every thousand times an advertisement is displayed.  For example, if an advertisement is displayed 3000 times (3000 impressions) and results in $30 in sales, the ad is said to have an RPM of $10.  In case you were wondering, the M in RPM refers to the Roman numeric symbol for 1000, just as V is 5, and X is 10.