The verse "Jehoshaphat made peace with the king of Israel" (1 Kings 22:44) means that Jehoshaphat, the king of Judah, entered into a friendly and non-hostile relationship with the king of Israel, whose name was Ahab in this particular chapter. This peace went beyond merely ceasing hostilities; it implies a formal agreement or alliance.

Here's a breakdown of what that likely entailed:

Cessation of Hostilities: No more warfare or border skirmishes between Judah and Israel.
Alliance: In this specific instance, it led to a military alliance, where Jehoshaphat agreed to join Ahab in fighting against the Arameans to reclaim Ramoth-Gilead (as the rest of the chapter describes). This shows the depth of the "peace."
Trade and Cooperation: While not explicitly stated in this single verse, peace often allowed for increased trade and cooperation between the two kingdoms.
Political Stability: By resolving conflicts, it brought a degree of stability to the region.

Important Considerations:

Jehoshaphat's piety: Jehoshaphat was generally a righteous king who sought to follow God. However, his alliance with Ahab, an idolatrous king, was heavily criticized (as seen in the rest of the chapter and later chronicles). This alliance compromised his commitment to God and led to negative consequences.
Context is key: This verse should always be interpreted in the context of the entire chapter and the broader historical narrative of the books of Kings. The rest of the chapter highlights the dangers of Jehoshaphat's alliance with Ahab, as it led to Ahab's death and nearly cost Jehoshaphat his own life.

In short, while "peace" sounds positive, in this specific biblical context, it represents a compromise of principle that ultimately led to negative consequences.