Programming Languages
For many people we learn programming languages from a very early age and the programming we learn in either collage or universities tends to be the one we show most interest in or willing to learn.
I would say the most popular languages for many would be PHP and ASP this is just due to it being widely taught and recognised across the world.
If we was to go more into detail we may look into other stuff such as C & C++ these are more complex however will be surprised just how much things uses this type of coding.