So with regard to lifespans:
Mean life expectancy would be the average age at death,
Median life expectancy would be the age which 50% of people will die prior to reaching, and which 50% of people will live past, and
Mode life expectancy would be the most common age at death.
Here is the frequency of male deaths by age
Thus, from this chart we can see the infant mortality is significant, that the average/mean age at death is 76, the median age is just past 80, and the mode is 86. As would be expected, if you reach a certain age, say 60, these number shift to the right a bit - if you make it to 60, the average/mean becomes 81.5, the median becomes 82.5 and the mode becomes 89. And the numbers for females are several years higher. Of course these shifts to older ages have a finite limit since everyone dies sooner or later!!!