Electric circuits are different than electronic circuits.
Schematics use symbols to represent components in the circuit. Conventions are used in a schematic to represent the way electricity flows. The common convention we use is from the positive to the negative terminal. The realistic way electricity flows is from the negative to the positive terminal.
The user of the device could become a part of the devices electrical circuit by providing a return path for the electrons through the users body instead of the circuits earth ground. When our body becomes part of an electrical circuit, the user can be seriously shocked, or even killed by electrocution.
A load of an electrical circuit may be as simple as those that power home appliances like refrigerators, televisions, or lamps or more complicated, such as the load on the output of a hydroelectric power generating station.