What they are "talking about" is the labor force participation rate. The percentage of Americans working is way down under this President! Part of that is simply a lack of jobs...part of it is a massive increase of people going on disability (because they can't find work?) and part of it is the Baby Boomers retiring which was expected.
Yes, and also people spending more years in school. The labor participation rate includes everybody between 16 and 65 years of age, so more people finishing high school, more people going to college and more people getting graduate degrees have all steadily pushed the labor participation rate down.
It's been falling since the 1990s at a fairly steady rate, not just under Obama. Mostly for those two reasons- more people in school and baby boomers retiring before they turn 65.