Running a Thick Client on a computer runs the client software components, plus the application server software components, and connects via ODBC to an APM database, usually on a separate computer.
APM Product direction is to phase out the requirement of running a thick client in admin mode for administrative tasks and customizing the application.
Important features such as sharing configurations have been made accessible on the Smart Client; however, there are still a few features that are still only available with thick client:
VSTS - 191592 - Allow modeling reports, forms and maybe even schema from the Smart Client