Text Excerpt:

Paragraph 1: A firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules.

Paragraph 2: When a packet arrives at the network boundary, the firewall inspects its source IP, port number, and protocol. If the packet matches safe rules, it is permitted to pass. Otherwise, it is blocked.

What is the structural classification of Paragraph 2 in an explanatory text?