Under a "breakdown" warranty, coverage is extended only to parts that break. Such a policy can prove less inclusive than is desirable, since not all parts fail due to breakage. Some need to be replaced because they've worn down over a period of time; a "wear-and-tear" warranty extends coverage to worn-down parts in need of replacement. Notice the careful language common to "breakdown" contracts:

"Breakage or total failure of a component/part making it unable to perform the function for which it was designed solely due to its condition and not due to the action or inaction of any non-covered part(s). Failure does NOT include the gradual reduction in operating performance caused by normal wear or use of the components/parts."