A Marketo custom object allows for the creation of a one-to-many relationship between your Marketo Leads and the custom object records. When the Marketo custom object is successfully provisioned in your account, you can:
	 
	Create/Read/Update/Delete records in the custom object via Marketo SOAP API
	Use smart list trigger when new records are added to the custom object
	Use the custom object data as a filter in smart lists (segmentation)
	Use the custom object data in emails using [Marketo email scripting]
	Reference: 
Getting Started