You distinguish the user access privileges from their license types. Client user (studio or named) can access any portal and perform its functions. But a portal user cannot log in to the smart client. If the dispatcher user wants to dispatch tasks from both client and portal, then he/she has to have one of the aforementioned license types. Then, that user can log in to both smart client and technician portal for task dispatch. The FSM 6 technician portal has the capability to allow assignment of techs to tasks. In other lower versions of technician portals they can only assign tasks to themselves, even though the user is a team lead.

FSM Smart Client is the Windows based application. This needs .Net framework to run. There is Smart client portal also which is designed to load on the browser as a thin client (from FSM 5.7 Onward). Smart client portal ( usually called as web portal), is designed to perform similar kind of task as Smart client but it has few limitation such as you cant do UI designing, client script design in web portal. 

Most of the core functionalities are working and the UI also looks similar. ( you can do all of other task than designing the application). For example, you can change application parameters, code table values, handle RMA, handle request and etc in web portal as well. But if you want to do UI designing and client script designing, you should use Smart client.

in smart Client

Web portal

Additionally, there are few other portals as Dhanushki mentioned in her comment. those are Warehouse portal, Tech Portal, Customer Portal and Dealer portal. Those portals are design to do specific functionality only and there are license types also to limit access to these portal users with smart client users. 

E.G if the user has custportal license, he cant login to smart client or webportal. he can login to customer Portal only.

I hope this is clear to you. please comment if you need any more information.