Mini Pagelayout in Salesforce allows you to choose the fields and related lists that will display in the mini view of the console.
You can define mini page layouts for the records that appear in the mini view of the Agent console, hover details, and event overlays. A mini page layout contains a subset of the items in an existing page layout. Mini page layouts inherit record type and profile associations, related lists, fields, and field access settings from their associated page layout. The visible fields and related lists of the mini page layout can be further customized, but the other items inherited from the associated page layout cannot be changed on the mini page layout itself.