I think it should be vwf not wvf. :) Yes, you're right. The vwf file is a text file which contains a set of input stimulus into your design. When you run the simulator, it takes in this input stimulus and display the results in the waveform. It has it's own format and it only can be used by QII Simulator. That's why running QII simulator requires the vwf. You have to view the waveform to see the result.
As for Verilog test bench, it is also a text file but is written in the Verilog language. Using the verilog language, you can write the input stimulus as well. Not only write input stimulus, you can do more than that (e.g. write a checker and verify your simulation results without viewing the waveform and etc). Basically writting testbench has a lot of flexiblity over the vwf. It is a language by itself unlike vwf contains just only the plain data (input stimulus). The tesbench you write is also generic which normally can be used by all third party simulation tools (e.g. Modelsim, VCS, NC-Sim).
Hope it helps.