what does intermediate switch mean in electrics

You will only need an intermediate light switch if you have lights that switch on and off from 3 or more places, for e.g. 3or more different dorways into/out of a room/hallway.

If you have lights that switch on and off from 2 places, then it is 2 way switches that you will need.

woodglass...

Intermediate switches are used, for example, in a three way lighting system that you might have in your hallway and landing. You might have a "normal" switch at one end of the hall, one upstairs, and an intermediate switch by the front door.

One-way switches are on/off. Two-way switches are used where you need two switches controlling the same light, e.g. two entrances to a room, top and bottom of stairs etc. One or more intermediate switches can be wired in between two two-way switches where you need more than two switches controlling the same light. In my flat I've got this: switches by the living room, bedroom and front doors, any one of which operate the same lights.