Crystal Planes: Definition & Meaning

[Hymne]

I think I understand the meaning and definition of the concepts of basis, cells, primitivecells and lattice, and so on. But could somebody please give me a short and consistent definition on crystal planes?
For example on which level do you mean when you talk about these planes? Are they planes of basis or planes of ions inside basis?

 

[Astronuc]

Crystal planes refer to 'planes of atoms' with some regular structure or array, as one would observe if the diametral planes of spheres representing that atoms were coplanar, i.e. they have the same geometric arrangement/relationship.

In reality though, there are missing atoms (and dislocations) and interstitial atoms. See - http://en.wikipedia.org/wiki/Dislocation

 

[Gokul43201]

Crystal structure = lattice + basis
Crystal plane = plane passing through lattice points

 

[tjtao]

All lattice points are on a series of planes(Crystal plane),Crystal planes are equally separate with each other.