eCpm is the estimated price you will be payed for each 1000 page views. If you are using the 'advertise on this site' link and someone buys advertising through you link, then you are paid for impressions you show.
WoW for the site I have it might be worth having a link about advertising on our site using our google "advertise on this site" link... So for each new advertising my site brings into adwords I get paid after 1,000 impressions?
It doesn't matter if you bring them into ADwords. Most Adwords advertisers are already veterans who search out sites to advertise on. The "advertise on this site" link makes it easier for noobs. But yeah, you get paid per 1,000 impressions. In my experience, it doesn't begin to compete with what you can get paid per click with relevant ads.
What do you mean by impression? Does it mean the traffic in your site? Does it mean 1000 unique visitor or 1000 number of visits? Sorry im a newbie to adsense.
impressions means how many times the ad is shown. 1 person can generate 10 impressions if s/he: 1) visits 10 pages 2) visits a page and refreshes it 10 times 3) any other example between the two ends mentioned above
It all varies, and people probably won't give you a lot of hard numbers, since google's TOS is a bit strict in regards to what details you can and can't release. For example, nobody will be allowed to tell you they got X clicks at $X per click with a clickthrough rate of X% for a total of $X. Typically, unless a few advertisers are into a bit of a bidding war on your site, your earnings will be lower when it's impression based, for the simple reason that it's not guaranteed traffic to their site, so most advertisers will not risk paying a heck of a lot for it, as opposed to paying per click which *is* guaranteed traffic for their money. That said, if you have an extremely low click-through rate to the ads on your site, then the impression based ads (if you manage to get them) will probably do better for you. Then again, most advertisers aren't going to run ads on your site for long if they're not getting clicks.
Not really. CPM ads compete with CPC ads (based on eCPM) for placement. Look here for more info: How do site-targeted and keyword-targeted ads compete?