Symbol 2 of Figure T6-1 represents a fixed resistor.
A variable resistor or potentiometer changes its resistance when its slide or contact is moved.
Symbol 1 in Figure N6-1 represents a fuse. You use a fuse to create an open circuit when there is too much current in a circuit.
Symbol 4 in Figure N6-1 represents a single-cell battery. A battery has a positive and a negative side.
Symbol 1 in Figure N6-2 represents a single-pole, single-throw switch.
You use a double-pole, single-throw switch to switch two inputs at the same time, one input to one output, and the other input to the other output.
A tolerance rating of 0.1% would indicate a high-precision resistor.
You would use a large size resistor instead of a smaller one of the same resistance value for greater power dissipation.