External Variables refer to the option to include two 'free' variables when you create your own custom automation rule.
When creating Optimization rules in the 'Automation Rule' section of adCore you have two modes to select from: Simple Mode and Advanced Mode.
(For more information on how to use Simple Mode please see THIS article)
You can use external variables ONLY when you are in 'Advanced Mode'.
These variable are useful to creating rules that can be customized for each campaign, without having to create a new version of the rule from scratch.
If you need to create a rule that will cap keyword bids at a certain maximum bid, but for each campaign you need a different cap value. (Campaign 1 needs to be capped at $1.5, Campaign 2 needs a cap at $4 etc.) Use one of the free values (Var1, Var2) in your rule as a placeholder for the cap value. Once the rule is created, add the rule to each of your campaigns, but define the value of the variable differently for each campaign.
Let's look at an example of a simple rule that uses an external variable or 'free variable':
What this rule does is increase the bid by 20% (take the current Max Cpc Bid and multiply it by 1.20)
When will this increase the keyword bid? When the number of clicks is greater than variable 1 (kwClicks > Var1)
As you can see in the rule itself we use the syntax of 'var1' or 'var2' to indicate the action we want to do on the variables.
Above the 'Set' box we have the option to select how many Free Variables we need: In this case we are only using var1. (note the check box next to the var 1)
We also need to make sure we name the variable, so that it easy to remember what type of value we want to fill in when we add the rule to the campaign. In our case, we are looking to know the number of clicks the keywords need to have, so that the rule will take effect.
After saving the rule, but before we add it to a specific campaign, you will see that the rule will prompt you for a value for 'No. of Clicks':