It sounds like the data you are looking at is in a report like an email performance report. These reports are meant to provide you a broad overview of how your message impacted its intended audience rather than getting granular and saying who was affected. To get the "who" data you will need to build a smart list to ascertain this information. An example smart list you can build is "sent email" "opened email" "clicked link in email" "sent email and bounced" and on and on... This is a rather basic functionality of the platform so I recommend you dive into the marketo documentation to insure you have a firm understanding of some of the fundamentals.
If you ever get stuck the community is here to help!
You'll need to pull smart lists if you'd like a list of names. The report doesn't allow you to drill in to see the list.