Cost per thousand, also called cost per mille, is a marketing term used to denote the price of 1,000 advertisement impressions on one webpage.
Cost Per Click refers to the actual price you pay for each click in your pay-per-click marketing campaigns.
CPL, is an online advertising pricing model, where the advertiser pays for an explicit sign-up from a consumer interested in the advertiser's offer.
CPA is an online advertising marketing strategy that allows an advertiser to pay for a specified action from a prospective customer.