What are the differences between the U3 and U6 unemployment rates?

Go to the Bureau of Labor Statistics (http://bls.gov) and find the current:
labor force participation rate
the U3 (Headline) unemployment rate, and,
the U6 unemployment rate;
What are the differences between the U3 and U6 unemployment rates? Note not only the unemployment rate percentages, but also who is counted in each of the two measures.
After examining the information and views found in the above activities, what factors are contributing to the current unemployment rate and the current labor participation rate? Support your view with data from the BLS, information

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