Hi; everyone! I am reading a book on macroeconomic. In the section of "Measure of Cyclical Variation in Output," I have poblem of understandig a sentence. The context is here: "Most of the analysis in this book focuses on short-term or cyclical movements in output and employment--fluctuations over periods of perhaps one to four years. In these short-term periods, fluctuations in output and emploument come primarily from variations in actual output around potential output, where potential oupput is defined as the level of real output that the economy could produce at high rates of recoursec utilization." (notice that the bold is made by author, not by me) I don't understand the second long sentences. For example, what does "come primarily from variations in actual output around potential output" mean? And I don't know the idea of "potential output" here either. Can someone informed of macroeconomics give me a hand? Thanks for your kind attention.