For the latter, bills have been paid long ago (sunk costs), titles are carried in inventory at or close to zero cost, and direct mail campaigns will create a low cost of goods sold and will be able to sustain a lower rate of response.
A browser is software that is used to access the internet. A browser lets you visit websites and do activities within them like login, view multimedia, link from one site to another, visit one page from another, print, send and receive email, among many other activities.
WebKit is used as the rendering engine within Safari and was formerly used by Google's Chrome web browser on Windows, macOS, iOS and Android before version 4.4 KitKat (Chrome only used WebCore, and also incorporated its own JavaScript engine called V8 and a multi-process system).