VNet Peering: Virtual network peering enables you to seamlessly connect two Azure virtual networks. Once peered, the virtual networks appear as one, for connectivity purposes. There are two types of VNet peering.

Regional VNet peering connects Azure virtual networks in the same region.
Global VNet peering connects Azure virtual networks in different regions.

A VPN gateway is a specific type of virtual network gateway that is used to send encrypted traffic between an Azure virtual network and an on-premises location over the public Internet. You also use a VPN gateway to send encrypted traffic between Azure virtual networks over the Microsoft network.

Site-to-site connections connect on-premises datacenters to Azure virtual networks
VNet-to-VNet connections connect Azure virtual networks (custom)
Point-to-site (User VPN) connections connect individual devices to Azure virtual networks

There are two types of load balancers: public and internal.

A public load balancer maps the public IP address and port number of incoming traffic to the private IP address and port number of the VM. Mapping is also provided for the response traffic from the VM. By applying load-balancing rules, you can distribute specific types of traffic across multiple VMs or services. For example, you can spread the load of incoming web request traffic across multiple web servers.

An internal load balancer directs traffic to resources that are inside a virtual network or that use a VPN to access Azure infrastructure.

Application gateway: There are two primary methods of routing traffic, path-based routing, and multiple site routing.

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Gateway transit
You can connect to your on-premises network from a peered virtual network if you enable gateways transit from a virtual network that has a VPN gateway. Using gateway transit, you can enable on-premises connectivity without deploying virtual network gateways to all your virtual networks.

Overlapping address spaces
IP address spaces of connected networks within Azure, between Azure and your on-premises network, can’t overlap. This is also true for peered virtual networks.

A is the host record and is the most common type of DNS record. It maps the domain or hostname to the IP address.
CNAME is a Canonical Name record that’s used to create an alias from one domain name to another domain name.
MX is the mail exchange record. It maps mail requests to your mail server, whether hosted on-premises or in the cloud.
TXT is the text record. It’s used to associate text strings with a domain name. Azure and Microsoft 365 use TXT records to verify domain ownership.