Hello manisivam

1. Earth is the electric potential of the local ground in the immediate area of an earth electrode.
2. Ground is exactly the same as (1) above
3. Neutral is the star point of a mains-voltage 3 phase system, which is connected to the Earth or Ground connection at the transformer. In the case of a M.E.N. (Multiple Earthed Neutral) system, the Neutral is also connected to an Earth/Ground connection at each Switchboard. This leaves the other wires from the mains transformer at a potential above Ground/Earth, and they are generally called "Phase" or "Active" wires - the ones from which you may receive an electric shock.
   

4. A Fuse is a metal wire/wires, enclosed generally in an insulating case/enclosure, which melts and breaks the connection after it passes more than the designed continuous current for the fuse.

5. A Relay in electrical terms, is an assembly of (generally) insulated copper wire, wound on an insulating bobbin, over a soft iron core, which has a moveable armature pulled away from the end of the soft iron core by a spring. When the coil is energised, the magnetic field attracts the armature, pulling it towards the end of the soft iron core. There are contact sets insulated from each other and the core/coil, and the movement of the armature may close/open or change-over contact sets. In this way, the originating voltage operating the coil/core/armature, is totally isolated from the contact sets, thus it relays the instruction and may control other circuits.

In the diagram at left, the switch operates the relay, which in turn operates the motor, via the contacts clearly shown.

More complex relays may have several sets of contacts:

• Make
• Break
• Make before break
• Break before Make
• Changeover
• Compound contacts = mixtures of the above.
  

Hope that assists you.

Kind Regards....