Instead of a longer article, I went for one article per structure.
Here are the others:

Hoof Wall
Frog & Collateral Grooves
Heels & Heel Bulbs
Coronary Band & Periople Skin


It is actually not pure white. It can lead to confusion because the internal wall is a starker white than the white line. It is located between the internal wall and the sole and its role is to maintain them both together. It also serves as a barrier from external intruders (bacterial or stone like) and protects the corium and coffin bone.

It is however a softer material compared to sole or wall material, and, when unhealthy, becomes an easier entrance for unwanted trespassers. This can lead to more serious infection problems and lameness.

This is what a tight white line should look like: golden colour between sole and wall, forming a shallow groove.
This is stretched white line and a lamellar wedge at the toe, caused by founder.
This is a very compromised white line, probably due to mineral imbalance and lack of movement.
This is a bacterial infection progressing via the white line, softer and weaker spot of entry, compared to the wall or sole.