Answer:
Given that
[100] :
It means that y and z component is zero.It is only in x direction.
[110] :
This is in x-y plane.Because z -component is zero.
[111] :
This is in a space because it have all three directions.
We take x is positive in right side ,y is positive in upward direction and z is positive perpendicular to paper .
The following diagram we can easily understand the following directions.
