What are ad impressions on Wizzley?

I've had an email today to tell me that my share of ad impressions has been raised to 55%.  This was followed by the exhortation to Go for Gold! 

Can anyone tell me what ad impressions are and what happens if I get to gold.  Is there a financial reward?  That would be nice as I haven't had a penny yet!

You must have over 50 articles now... read more about the Ad impressions and earnings onMaking Money on Wizzley: Impressions, Clicks and Sales

It basically means you can now earn more of a percentage.

Thanks for replying and apologies for not catching up with this before now.