This is the 267th most frequent German word.
ländern
"Ländern" is the dative plural form of "Land," meaning "to (the) countries" or "to (the) states."
Here, "Ländern" is in its dative plural form, used to indicate the locations "in various countries."
In vielen Ländern spricht man mehrere Sprachen.
In many countries, people speak multiple languages.
In this case, "Länder" is the plural of "Land" in nominative case, referring to "countries."
Die Kinder lernen in der Schule über die Länder der Welt.
The children are learning about the countries of the world at school.
Here, "Länder" refers to "countries" in the accusative case, indicating the destinations of travel.