The ''Title'' of ''Walker'' is related to the fictional ''World'' of ''The Walking Dead''. Initially a graphic Novel (comic book) series which ran from 2003 until 2019, the Worldwide popular series of books would spawn the International Hit Television series of the same Title (from 2010 until 2022), Several franchise spin-off series (some of which still continue) help ''flesh out'' a World devastated by a Zombie Virus. The overall cause of what causes ''Walkers'' was never really explored (on purpose). Writers wished readers to concentrate on ''how'' People of different walks of life (good and bad) interact in such a World where ''survival'' becomes warped at times.
Also called ''Biters'' and ''Rotters'', ALL Humans apparently have the latent ''Zombie Virus'' in their DNA. Perhaps it was ''always there'' – waiting on the right combinations of biological events to cause it to react. When a Person ''dies'' (as long as the brain or spinal cord is NOT damaged), Their ''upper brain functions'' cease. What is left (and what the virus activates), is the base ''animal instinct'' all Humans have. The other downside to reanimation is ''The Hunger''. Walkers crave flesh (all kinds) to consume. Walkers do NOT need food to survive as ''living'' people do – it is simply ''instinct to feed''.
Walkers are above all things dead Humans. They cannot reason or understand (let along communicate). As such being dead, They decompose. Unlike a ''normal corpse'' which decomposes at various length (depending on environmental factors), The Virus seems to retard this process. While a normal body under optimum condition may be rendered into a natural biological state in 1 to 3 months (skeletonization), it may take a Walker 6 months to 1 year to finally ''die''. Once muscle tissue is eroded, and without such tissue to create movement (skeletal),The Walker will ''lay there'' until even it's brain decomposes and as such ''kills'' the Virus.
Walkers are also extremely hard to kill (again), Only after extreme heat (burning) or explosion will immediate death happen. In both graphic novel and Television series, the ''sure fire way'' to kill a Walker is to either decapitate the head or pierce the brain. This will instantly kill a Walker. Owing to the many franchise additions which are soon comings, Walkers will still occupy Our ''nightmares'' for many more years to come!