What the economy produced, quoted at an annual rate. Nominal is what was spent, real is what was bought, and the ratio between them is the price level. GDI counts the same economy from income received, and PDFP keeps only private domestic demand.
BEA via FRED · quarterly output and income at an annual rate, nominal, in chained 2017 dollars, and with private final sales beside them · price level computed here
This page draws an interactive chart and needs JavaScript. The data is published by the US Treasury and the federal statistical agencies, most of it obtained through FRED.