Trying to understand the jargon

Have never touched on this before. Can anyone let me know, or point me in the right direction, to know what the following stands for and a brief explanation of them please?
CPM
PPC (pay per click)
CPC (cost per click)
CPA
CTR

Any help appreciated.

Dez

CPA - When referred to in Affiliate circles it generally means Cost Per Acquisition, i.e. what you calculate that you have had to spend through PPC or a banner campaign to achieve a sale. Confusingly it can also stand for Cost per Action within the advertising world.
CPM - Meaning Cost Per Thousand. This is an industry standard for selling banner adverts. The M is from the Roman for thousand.
CPC - Meaning Cost Per Click. Certain search engines allow advertisers to pay to achieve top listings in the search results at a specified cost per click. To do this you will want to target pay per performance search engines that have the broadest reach and can drive traffic for minimal cost a click in order to best use your SEO resources. Placement within Overture.com is presently one of the most cost-effective solutions to reach your targeted audience. Begin by selecting the search terms that are relevant to your online business, set what you would like to pay on a per-click for each term. The higher you ‘bid’, the higher in the search results your business is likely to be. This is generally seen as an economical method to rank high on search engines, augmenting search engine directory submissions.
PPC - With Pay Per Click an advertiser pays an agreed amount for each Click through to the Merchants’s site.

i found few of them,might this will help you.

Many thanks for that, much appreciated. Now know CTR is Click through rate, just trying to find a good explanation of it now.

I have found the explanation,may be this would clear your concept.

Click-through rate the ratio of the number of times a user clicks on an online advertisement per number of viewers who view the Web site that has the advertisement on it. For example, if one out of 100 people who visit a specific Web site click on an advertisement and are taken to the advertiser’s site, then the CTR of that advertisement is 1/100, or 1%.

You can find more details on wikipedia.com