Hi Piyush,
To access the token for a field, use one of the following methods:
Access the static member variable name of an sObject static type, for example, Account.Name.
Call the getSObjectField method on a field describe result.
The field token uses the data type Schema.SObjectField.
In the following example, the field token is returned for the Account object’s Description field:
Schema.SObjectField fieldToken = Account.Description;
In the following example, the field token is returned from the field describe result:
// Get the describe result for the Name field on the Account object
Schema.DescribeFieldResult dfr = Schema.sObjectType.Account.fields.Name;
// Verify that the field token is the token for the Name field on an Account object
System.assert(dfr.getSObjectField() == Account.Name);
// Get the describe result from the token
dfr = dfr.getSObjectField().getDescribe();