In virtual networking, virtual machines have virtual Ethernet adapters that connect to Virtual Switches. Everything found in a physical Ethernet adapter can be found in a virtual Ethernet adapter, and everything found in a physical Ethernet switch can be found in a virtual Ethernet switch.
Essentially, a virtual Ethernet adapter is an emulation of the physical Ethernet adapter. Emulation is slow, so it is better to use an optimized paravirtualized Ethernet adapter. To take advantage of the performance gains in the paravirtualized adapter, you need to install the tools that are provided by the hypervisor manufacturer. Virtual network adapters have their own MAC addresses and unicast/multicast/broadcast filters and are strictly Layer 2 devices.