What is difference between internal and external load balancer listener with respect to azure (IaaS)
External - Uses the public Virtual IP address of the cloud service that hosts the Virtual Machines.     Use when you need to access the listener from outside the virtual network, including from the internet, i.e. public facing

Internal - Uses Internal Load Balancing (ILB) with a private address for the listener.  Use when you only access the listener from within the same virtual network. This includes site-to-site VPN in hybrid scenarios, i.e. not public facing