Dyanamic Appoval basically to allocate the Approver dynamically. Dynamic approval process is used to route approval requests to users listed in lookup fields on the record requiring approval. In this, approver names are defined dynamically from an object.

Implementation:

1. Create a lookup field to user in your object. Let the name be Next_Approver__c.

2. Write a logic to assign the approval to the user mentioned in that field using setNextApproverIds().

Check the below link for sample code for the step 2.

https://www.infallibletechie.com/2012/04/approval-process-using-apex.html

Cheers!!!