An "End User" is the one doing Data Entry (through pa30, pa40, CATS, etc.), executing processes (such as Time Evaluation, Payroll Calculation, Third Party Remittances, etc.) and generating reports (such as Quota Balance Statement, Absence Trends, Missing Infotypes, etc.).
An Internal SAP Consultant is the one that will debug problems that the users can't solve, make changes in the configuration to correct problems, to adapt to new collective agreements or legislation requirement, do "Unit Tests" after these changes, take an active part in the application of the HRSP (Service Packs) and their tests, take the lead in the Year-End update of Legal Changes, keep updated on the evolution of the software and prepare proposals for changes (like On-Site or Cloud Solutions), and so on.