Explanation
IaaS stands for Infrastructure as a Service, which is a cloud computing model that provides virtualized computing resources such as servers, storage, and networking over the Internet. IaaS can provide data storage, hardware options, and scalability to a third-party company that cannot afford new devices by allowing them to rent or lease the infrastructure they need from a cloud provider. The company can pay only for what they use and scale up or down as needed. References: https://www.comptia.org/blog/what-is-iaas

Explanation
PAT (Port Address Translation) is a type of Network Address Translation (NAT) that allows multiple devices to share a single public IP address by using different port numbers. PAT enables devices to access the internet without exposing their private IP addresses. A router is a device that can perform PAT by translating the source IP address and port number of outgoing packets and the destination IP address and port number of incoming packets. A Layer 3 switch is a device that can perform basic routing functions by using IP addresses, but it cannot perform PAT or other advanced routing features that a router can.