"However,outside the handful of countries speaking one of the half-dozen major world languages, few people on this planet have only one tongue. " Here are the main ideas: A small number (handful) of countries speak the most common languages of the world. People who do not live in these countries (and who do not speak one of the very common world languages, usually speak more than one language (tongue). I hope this makes sense.

People in countries that speak one of the six major world languages tend to speak only one language. In other countries people are much more likely to speak more than one language.

many people can speak one more languages