In Salesforce, the Master-Detail relationship can have a roll-up summary field, but the lookup relationship is not suitable for one. When we wish to display a value in a master record based on the values of a number of fields in our detail records, roll-up summary fields come in handy. However, the master-detail relationship must be connected to the detail records. The total number of detail records can be counted, summed, and the lowest or maximum value can all be determined by utilising a roll-up summary. visit:
https://www.iteducationcentre.com/salesforce-training-in-pune.php