CPM advertising — CPM stands for cost per mile. In English, it means the amount you will pay for every 1,000 impressions. (An impression means your ad has been viewed.) So, if a website says their advertising is $10/CPM, and you spend $500, your ad will receive 50,000 impressions.
CPC advertising — Cost per click advertising means you only pay when your ad is clicked on.
Flat Rate Advertising — Many content providers have a flat rate that they charge to advertise with them for a set amount of time. For example, a blog might charge you $100/week or $300/month.
When it comes to advertising it is not always more is more. It is more like what is going to get me the best bang for my buck. You can spend $500 on advertising, but if your ads are not visible to your target market it was a waste of money. If you spend $100 to advertise your knitting supplies on a How to Knit blog that is money well spent.
When investing in advertising take your time. Do your research. Advertising is a useful tool when done correctly.