If a distribution is ordered, the median divides this distribution into two equal parts.
Thus, for a distribution of wages, 50 % of the wages are below the median and 50 % above it.
A large number of economic values have a lower limit but not an upper one. For example, the hourly wage has a lower limit provided by the SMIC, but certain wages can be very high indeed. These high wages pull the mean upwards, despite the fact they are few in number, and the mean is therefore generally higher than the median.
Also, the uncertainty surrounding the extreme values, and in particular high values, has an impact on the mean but does not affect the median. In this respect, the latter is therefore a more reliable indicator.