Carpet is typically damaged slowly over time. The 3 primary types of damage are abrasion, packing, and incidental. Most damage can be prevented from continual care.
Abrasion is when the carpet fiber is scratched. This is typically caused when sand and dust is rubbed against the carpet by people walking across a dirty carpet. Abrasion can be avoided by regular vacuuming. Abrasion often happens in traffic lanes and cannot be fixed from carpet cleaning.
Packing is usually what happens in high traffic areas and is often more extreme when people wear their shoes inside. Packing is when carpet fibers is compressed over and over and loses its resilience. Packing may be helped by pulling the carpet back up by suction, by vacuuming, or by hot water extraction.
Incidental damage can be anything from a cigarette burn to a stain to a damaged carpet seam. Most often these types of damages can be repaired by a repair technician. Some carpet cleaning companies offer these services or may recommend reliable technicians.