Leads Detail Page -
As you click on a lead name then that particular lead open in full leads detail page which shows you detail, activity, and related tab.
Lead Details -
On the Details tab, you'll see all the default and custom fields you've chosen to display for leads. This gives you context for who the lead is and all the related information that you have added.
Lead Activity -
In the Activity tab, you'll see your interaction stats, which help keep you on track with the frequency of your communication. Below that, you have your activity log, where you can see the details of each interaction you've had with the lead and any updates that have happened on the lead record. You can also filter this log to see relevant events.
Lead Related -
To the Related tab, you can see the tasks, files, drive attachments and calendar events associated with this lead.