The NAT Target tab is a table that allows you to specify the target firewalls or device groups for each NAT policy rule on Panorama. This tab is available only on Panorama and not on individual firewalls. The NAT Target tab enables you to create a single NAT policy rulebase on Panorama and then selectively push the rules to the firewalls or device groups that require them. This reduces the complexity and duplication of managing NAT policies across multiple firewalls1. Reference: NAT Target Tab, NAT Policy Overview, NPTv6 Overview, Updated Certifications for PAN-OS 10.1.

Silently drops the traffic; for an application, it overrides the default deny action. A TCP reset is not sent to the host/application.
For Layer 3 interfaces, to optionally send an ICMP unreachable response to the client, set Action:
Drop and enable the Send ICMP Unreachable
check box. When enabled, the firewall sends the ICMP code for communication with the destination is administratively prohibited--ICMPv4: Type 3, Code 13; ICMPv6: Type 1, Code 1.
https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClltCAC#:~:text= The% 20Deny%20action%20will%20tear,packets%20will%20be%20silently%20discarded.

https://docs.paloaltonetworks.com/pan-os/8-1/pan-os-web-interface-help/network/network-zones/security-zone-overview