Bundesländer (note the spelling) is the plural of Bundesland.
A Bundesland is the German equivalent of what are called "states" in English speaking federal countries.
Germany is divided into 16 Bundesländer.
The official name is "Land" (plural "Länder"). But as this also has the same meaning as "Land" in English (as in England or Deutschland). They are commonly called Bundesland / Bundesländer, which translates as "Federal state" / "Federal states".
Bundeslaender in Germany are alike the states in USA with a strong federal constitution, including some sovereignty for the Bundeslaender. See also the two links I added.