Can i get easy to understand explanation regarding interstitial lung disease?

Interstitial: It means the area between the alveoli. That includes the blood vessels and the basement membranes, etc, anything not part of the alveoli itself. When there is an inflammation, it occurs in that area. The fibrocytes, part of the inflammatory reaction lay down fibers(scar), it thickens that area making the distance between the wall of the alveoli and the blood vessel farther, diffusion is impaired.