Spend – the budget you have to spend on ads.
Quality Score – Google’s determination of the relevance, quality and probable user satisfaction of your ads and landing pages.
Clickthrough Rate – [Ad Clicks/Impressions in the Adwords network]- a measure of ad and keyword effectiveness.
Conversion Rate – [Sales or Leads/Visitors via PPC] – a measure of ad, keyword, offer, and landing page effectiveness.
Return on Ad Spend – for each dollar spent on advertising, what is the return after all expenses.
Cost Per Lead – what does it cost for us to get a qualified lead (not sale) from our campaign. The sales process is still to be done.
Profit – [revenue – expenses (including product cost, ROAS, and overhead)]
Lifetime Value – the sales that might be expected from a typical customer over the lifetime of your business. Sometimes advertising buys must consider this for certain types of products.