Are you running a campaign and you want to know who came from which campaign? It is SUPER simple with the utm_source property.
What is the idea?
When creating your URLs in your google/facebook ads for example, add at the end
?utm_source=facebook_ad1
Indicating in this example that it is our first ad in facebook (of course you can add better names).
Now how to track that when someone registers or fills a form/checkout?
All we have to do is add these properties to our forms. Go in the form fields or the additional fields if it is a checkout or registration and add a Hidden Field with name being utm_source.
Then go in the settings of your field and map that field from the dropdown to the utm_source that we just created in the Contacts as a property.
That's all! Now when someone submits your forms and has the utm_source as a URL from which they came from, the value of the source will be recorded for the user and you will know where they came from.