Final answer:
In Marketo, you define segments that can be used in emails through the Email Editor.
Step-by-step explanation:
In Marketo, you define segments that can be used in emails through the Email Editor. The Email Editor in Marketo allows you to create and customize emails for your marketing campaigns. Within the Email Editor, you can define and manage segments, which are specific target groups based on certain criteria. These segments can then be used to personalize and send targeted emails to a specific audience.