Vbios is the video card equivelant to the Bios in your Motherboard. Warning: you can render your video card unusable by improperly flashing Vbios - the only real safe way to flash Vbios is to obtain the correct version from your video card manufacturer. There are many Vbios for a particular card as components change during the life-cycle.
In my case - I knew I had a problem somewhere because when I could not use Catalyst versions past 10.10. After 10.10 (11 series) the Catalyst and Drivers were changed signficantly. When I installed any of the 11 series Catalysts - I would experience "Grey" screens as my 5870 crashed. Many times a day.
I had purchased my 5870 very early on - so it had a very early Vbios installed. All Vbios have a date - and the one my 5870 came with was 12/17/09 (version 012.018.000.001.000000).
So, I went the the Sapphire website and filled out a trouble ticket. They responded and emailed me. They provided the correct Vbios in the email and some instructions. The newest Vbios for my particular 5870 is 012.020.000.001 - Date 2010/03/08.
How do you know what Vbios you have? Open up the AMD CCC and select the "Information Tab" - then select "Hardware". Scroll down the information window until you see "Bios Version/Bios Part Number/Bios Date". That's what you have inside.
So with all that said, if you aren't having obvious problems - don't worry about it.
I only point this out as a variable in the equation. Hardware, O/S, Video Drivers are what everyone normally focuses on, however Vbios can play a role.
Here's a GPU-Z screenshot of my current configuration:
GPU-Z is a good utility to monitor all sorts of stuff with your video card. It's free. Just Google GPU-Z, download - install and run
Hope this helps,
S!
Gunny