Nehemiah 12:20 is part of a larger list in Nehemiah 12 that details the priests and Levites who returned from the Babylonian exile with Zerubbabel and Jeshua (Sheshbazzar and Joshua). These lists are crucial for understanding the re-establishment of the temple service in Jerusalem after the exile.

Let's break down the verse:

"of Sallai, Kallai;" This means that from the family or house of Sallai, the representative or leader was Kallai.

"of Amok, Eber;" This means that from the family or house of Amok, the representative or leader was Eber.

In essence, this verse is simply documenting the head of each family or priestly division. The list is a roll call of the individuals responsible for leading their families in the revived temple service. Sallai and Amok were probably the founders of their respective families or priestly divisions, while Kallai and Eber were their representatives at this specific point in time.

Why are these lists important?

Genealogy and Identity: These lists helped establish and maintain the lineage of priests and Levites, ensuring the continuity of the priestly order according to Mosaic law.
Proper Temple Service: Knowing which families were responsible for which tasks in the temple was crucial for maintaining the proper order and function of the temple service.
Historical Record: The lists provide a valuable historical record of the return from exile and the rebuilding of Jerusalem.
Legitimacy: The list provided legitimacy to the priests and Levites performing their duties. They could trace their lineage back to pre-exilic times, confirming their right to serve.

In conclusion, Nehemiah 12:20, like the rest of the chapter, is a genealogical record that identifies the representatives of specific priestly families who were responsible for serving in the newly rebuilt temple in Jerusalem after the return from exile. It's a vital piece of information for understanding the reconstruction and organization of Jewish religious life during that period.