KNX Virtual is a Windows application representing a KNX installation, i.e. it is not a physical installation but it behaves like one.
The advantage is that no investment in hardware (i.e. KNX power supply, KNX/USB interface or KNX/IP interface, KNX devices) needs to be made in order to test and play with KNX & ETS.
This is a reference price, please check on Amazon