Dolibarr setup is done on 2 levels. First level is global (setup applies for every users) and second level is by user (setup applies for a particular user only).
Global setup (all users)
All global setup is saved into table llx_const. Each parameter is defined by a key (name of parameter) and a value in this tables. Other fields in this table are not mandatory. The field note contains a description of the goal of parameter. The field entity can be 0 or 1. It will be used to other value when a feature to save several instances of Dolibarr in just one database will be ready.
All this constants can be edtited from menu "Home - Setup" (every data in this menu and submenus are saved in this table). The page "Home - System Tools - Dolibarr - All parameters" can be used to view name/value pairs of all parameters.
By user setup
All setup particular to a user is saved into table llx_user_param. In this table, the field fk_user contains the id of concerned user. You will find also a key (name) and a value. Other fields in this table are not mandatory. The field note contains a description of the goal of parameter.
All thoose parameters can be edited from the user card, tab "User setup".