Genesis 10 is a genealogy, often called the "Table of Nations," which describes the descendants of Noah after the flood and how they populated the earth. Genesis 10:26 is part of this genealogy, specifically dealing with the descendants of Shem.

Here's a breakdown of what "Joktan became the father of Almodad, Sheleph, Hazarmaveth, Jerah" means:

Joktan: Joktan was a descendant of Shem, one of Noah's sons.
Became the father of: This phrase means that Joktan was the ancestor of the following individuals. He was their direct father, or he was the founder/patriarch of the tribes/clans that were named after these individuals.
Almodad, Sheleph, Hazarmaveth, Jerah: These are the names of Joktan's sons. These sons are often understood to be the founders of different tribes or clans in a particular region.

In essence, this verse is stating that Joktan was the ancestor of the tribes or people groups represented by Almodad, Sheleph, Hazarmaveth, and Jerah.

Significance:

Genealogical Record: This is part of a broader effort to trace the lineage of humanity after the flood.
Geographical Connection: Biblical scholars often try to identify the regions where these descendants settled. Some names have potential connections to geographical locations or tribal names in ancient South Arabia (modern-day Yemen). For example, "Hazarmaveth" is often associated with the Hadramaut region of Yemen.
Understanding Ancient Cultures: The "Table of Nations" provides insights into how the ancient Israelites understood the relationships between different peoples and cultures in their world.
Establishing Identity: Genealogies were important for establishing identity, inheritance rights, and social standing in ancient Near Eastern societies.

Therefore, Genesis 10:26 is not merely a list of names. It's a statement about Joktan's lineage and the origins of various people groups or tribes that were believed to be descended from him.