Your pet might be the biggest threat to your hardwood floor. Pet claws are usually harder than the polyurethane coating your floor and harder than the wood itself. That means that claws will scratch and dent the floor over time. Pet stains are another problem. Urine is the most common pet problem that stains the wood.
Hardwood floors need to be refinished from time to time to protect the wood itself. A polyurethane-finished hardwood floor is covered with coats of liquid polyurethane that dries to form a protective shell over the wood. Over time, that finish can be scratched, rubbed, and scraped away. The homeowner will then need to have the finish reapplied.