Parameters are maintained in the "Parameters" tab of transaction SU01. Parameters has nothing to do with the authorization. They are used to ease the daily life of a user. For example if the user is responsible with one customer, s/he adds kunnr parameter here, to have this customer id filled when s/he calls the related transaction.
The parameters are the user parameters they will be in the structure USPARAM and in the table TPARA. Parameter IDs are usually only used to memorize certain user-specific settings, e.g. whether you prefer the classic or the new ABAP editor / debugger, or some application-specific default values (e.g. the "customer number", KUNNR) which are used to fill-in corresponding entry fields (on selection screens / dynpros) automatically.