What exactly? An index (1982 = 100) that measures the change in prices received by domestic producers of commodities in all stages of processing (crude materials, intermediate materials, and finished goods).
Source: Labor Department
Released when? Around the 13th of the month at 8:30 Eastern. Data for prior month.
Market importance: High. Timely. All inflation measures routinely move markets.
Other notes: (a) The "core" PPI excludes the often-volatile food and energy sectors and gives a clearer picture of the underlying inflation trend. (b) The headline number is the percent change from the prior month, but we also graph the year-on-year change. That way you can see the rate at which wholesale inflation is increasing or decreasing.