What is the difference between open and close switch?

Answer 1

In an open circuit no cuttent can flow so the switch would have to be in the off position- the switch is open and not completing the circuit. A closed circuit is one where current can flow all the way through, the switch would have to on and therefore closed.

Answer 2

Current flow occurs when a switch is closed. When it is open there is no current flow, and thus no "work" by the resistance. Resistance may be a light bulb, electric motor, speaker, integrated circuit, etc.

For this reason closed = on, and open = off.