The simplest example to explain the difference between earned income and unearned income is to compare wages from consulting work and bank interest. The former requires your active participation and is earned income. Interest, on the other hand, are unearned (those of you who studied Marx in college will recall the struggle of capital vs labor - the IRS happens to agree), and not eligible for FEIE.
Income earned in the US means that even if you spend most of the year in Paris, but fly to New York to give a speech that earns you $10k, you are not able to utilize FEIE to exclude this income, as it is earned in the US. However - if you were to give the speech over Skype, while being physically located in Paris, you would be able to exclude that income.