Could someone give me an explanation what is the difference between physical and logical server environments (or architecture/framework)? Any practical examples?
A "logical" view of a system describes the functional or visible function / layout. Logically, four virtual machines appear to be four different computers. In network topologies, a logical topology often describes the paths that data can take across a network irrespective of how the wires are plugged into each other.
A "physical" view of a system describes the "stuff" that makes up the system, or describes how the system is connected together in the physical world. Four virtual machines may have a physical manifestation of running on a single server computer. The logical diagram that shows four computers, in this case, would reflect only a single computer in a physical diagram.
Networks that use VLANs or VPNs often have radical differences between their logical topologies and their physical topologies. Several remote sites "connected" via VPNs appear, logically, to be connected to each other with dedicated wires even though, physically, each site has only a connection to the Internet.
Likewise, diagrams of server infrastructures that use virtualization often have radically different logical and physical manifestations.
Ultimately, any system that has a difference in its functional versus real-world physical makeup will benefit from diagrams that describe the logical and physical separately (and that relate them to each other in a meaningful way).