This document discusses different types of unemployment: cyclical unemployment which rises during economic recessions, frictional unemployment which occurs as people transition between jobs, and structural unemployment which results from skills mismatches between workers and available jobs. The unemployment rate is considered the number of unemployed people as a percentage of the total labor force, and a rate of 4% or lower is generally seen as healthy, while higher rates can have negative economic impacts. Full employment is defined as utilizing all available labor resources efficiently rather than a 0% unemployment rate, with some frictional unemployment always present as people change jobs.