This verse refers to an incident where a giant, likely a Philistine, challenged or defied the Israelites. The verse states that this giant was killed by Jonathan, the son of Shimea, who was David's brother.

Here's a breakdown:

"When he defied Israel": This indicates that the giant was taunting or challenging the Israelite army or nation. This was a common tactic of the Philistines, who often used exceptionally large and skilled warriors to intimidate their enemies.
"Jonathan the son of Shimea": This identifies the person who killed the giant. Jonathan is the son of Shimea (also known as Shammah), who was one of David's brothers.
"David's brother killed him": This emphasizes the family connection between Jonathan and King David. It also highlights the bravery of David's family, who were willing to fight for their people.

Context and Relation to Other Texts:

This verse relates to the accounts of battles between the Israelites and the Philistines, particularly the stories involving giants. The most famous of these stories is, of course, David's defeat of Goliath. However, this verse indicates that other giants were also a threat to the Israelites and were defeated by other members of David's family.

It's worth noting that there are some discrepancies between the account in 1 Chronicles and the parallel account in 2 Samuel 21:19. 2 Samuel attributes the slaying of the giant to Elhanan, the son of Jaare-oregim, not Jonathan. Biblical scholars have offered various explanations for this discrepancy, including:

Scribal error: That a mistake was made when copying one of the texts.
Different giants: That Jonathan killed a different giant than the one killed by Elhanan.
Elhanan's alternative name: That Elhanan was also known as Jonathan, or that he was the son of Shimea.

Regardless of the exact details, the verse in 1 Chronicles 20:7 serves to illustrate the ongoing conflict between Israel and the Philistines and highlights the courage of David's family in defending their nation against their enemies.