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

• Hoof Wall
• Sole
• Frog & Collateral Grooves
• White Line
• Heels & Heel Bulbs
• Coronary Band & Periople Skin

BARS

They are proper wall extensions (both inner and outer walls) growing from the corium just next to the frog.
On healthy feet, they should stop around the middle of the frog, look solid, parallel to their side of the frog and rather up-right (not looking like they’re sleeping flat on the sole). They should blend flawlessly into the heels.

They protect the back of the foot from extreme distortions, control its movement and add resistance to the heels. On healthy feet, when nice and upright, they can act as great studs on slippery grounds when left slightly above sole level. In some cases (depending on hoof health, ground and use of the foot) they have a vertical support and energy dissipation role.

This is a strong and healthy bar.
A foot with the excess bars marked up on the 2nd picture. The blue marks are where the bars actually finish on this foot, green marks are where they should finish. The excess length is marked with the yellow line.
Overgrown and laid-over bars. They are not supporting the back of the foot.
Bars migrating to add a protective layer to the sole.
Almost absent bar.