In reply to milinraijada:
This is explained in section 13.4.4 Background processes spawned by function calls of the IEEE 1800-2012 LRM. See Get your free copy of the IEEE 1800-2023 SystemVerilog LRM - Verification Horizons to get a free copy.
The motivation for this feature was to allow a class constructor (which is a function) to start a thread. In most methodologies, like the UVM, you would never use this feature.