Answer:   Determine whether users have access to records they don’t own, including records to which they don’t have sharing access, but someone below them in the hierarchy does.
Say there are three roles
• Role A
• Role B
• Role C
Role A is higher in hierarchy, Role B is in middle and Role C is lower in hierarchy
If the Role A user through Manual Sharing or Sharing Rules, shares the record to Role C user who is in lower hierarchy, then the Role B user who is above in hierarchy to Role C user can see the records, if we enable Grant Access Using Hierarchies at sharing settings else Role B user cannot see the record.