eCPM: The "effective cost per thousand" is calculated by taking total earnings, dividing it by the number of impressions served and then multiplying it by 1,000.
CTR: The "click thru rate" is the number of times an ad was clicked divided by the number of impressions served (and multiplied by 100 to express as a percentage).
CPC: The "cost per click" is calculated by taking the total money spent divided by the number of clicks received for a campaign.
eCPA: The "cost per acquisition" is calculated by the campaign cost divided by the total of impressions served multiplied by the CTR multiplied by the conversion rate. The "effective cost per acquisition" tells you what you would have paid if you had purchased ad inventory on a "cost per action" basis (as opposed to a "cost per click" or "cost per impression").
ACONV: Assisted Conversions are events when a user clicks or views an ad from one of your campaigns, but then later clicks or views an ad from another campaign and converts. In this situation, normally the second campaign would be credited with a conversion and the first campaign would get nothing, but the reality is that the first campaign played some role in the user's path to conversion and that should be recognized in some way. For more information and examples, see this article.