Why there are differences between the unemployment rate of the US between the data of the bureau of labor statistics and the ILO (international labor organization). Have they different definitions of labor force? Or is it because they are conducted by the different organizations?
With regards to the concept of 'unemployment' and the 'unemployment rate' it is important to note that, while the general definition (number of unemployed /number labor force * 100) is pretty standard, the exact parameters or "operational criteria", in ILO-speak, for how some of these concepts are defined can vary from place to place, often with large impacts on the final statistic.
Specifically, it is important to consider the criteria what is used to classify people as "employed" and "unemployed", with the latter concept having many different criteria to define--e.g. working age, paid or not, what constitutes "actively looking for work", what constitutes "available for work", etc.
With this in mind, the ILO has a standard definition with specific operational criteria for all of the concepts used to define employement, unemployment, and the labor force, so that calculations of the unemployment rate using this ILO definition are sure to be comparable from place to place.
Now with all of that said, the US BLS uses the Current Population Survey to calculate unemployment rate according to the ILO definition, so the stat should be the same. If you go the the ILO-STAT dashboard for the United States, you can see that the data-source for ILO stats on the U.S. is in fact, the BLS and the US Current Population Survey.
On a more general note, the ILO recently published this very useful, concise guide that explains specifically l their definition, but also, more generally, how to interpret uemployment rates and all of operational criteria and how they can impact rate calculations. You can find the guide to unemployment rate on the ILO site.