In that state (of etheric purity), the intellect is filled with truth or, the gyan of truth dawns.

There is just one truth, reality, that which is eternal, or constant. Rest everything around, all that we see, touch, smell, taste, hear or think is unreal, the body too is unreal, it is temporary and constantly fading away.

When the etheric layers are purified, then the intellect reflects upon that truth or reality.

The difference between a yogi and others is that the yogi is stilled on the real, others are immersed in unreal.