# Metrics in online advertising

There are quite a few metrics in online advertising. Some of them are easy to understand. Some are not.

Here you'll find definitions of both the easy ones and the not so easy ones.

## Definitions

What is really the difference between CPM and eCPM? And is really CPM a metric or a payment model in online advertising?

Buying methods explained

Definition of CPM

Definition of eCPM

## Calculation methods

And how do we calculate these metrics?

How to calculate CPM

How to calculate eCPM