CPC is the abbreviation for Cost Per Click. This term has to do with online advertising where the advertiser pays for each click on an ad. This ad may consist of a banner, image ad, link or text ad. The amount the advertiser has to pay for one click is called the CPC. CPC is also called PPC: Pay Per Click. There is a slight nuance difference here, though. PPC is primarily used when you are a provider of the advertising model and CPC when you are the advertising party.
CTR is the abbreviation for Click Through Ratio. This shows a percentage that indicates how much a link or banner is clicked. You calculate the CTR as follows: (number of clicks / number of impressions) X 100 = CTR. The CTR is a signal to Google indicating how well your page matches the search query. When it matches well, it means Google will give you a higher ranking in search results. After all, Google wants to keep the user happy, so shows the best results in searches.
Finally, CPM. CPM stands for Cost Per Mille. This is an online payment model for ads. It is also sometimes called Cost Per Thousand. The amount attached is the amount the advertiser pays per 1,000 impressions. When you plan to advertise online, you will, without fail, have to deal with this abbreviation.