How to change symbol size, line thickness and the like in Gnuplot?

How to change symbol size, line thickness and the like in Gnuplot?

- Various commands are available to assign line and point properties.

- These properties include color, thickness, shape of point etc.

- The command test displays a test page for the selected terminal type.

- The test page shows all available pre-defined combinations of colors, size and shapes.

- The command ‘set style’ is used to define the combinations.