Samsung SGH-x427 User Manual page 188

Glossary
browser is not actually connecting to the web server. The
request from their browser goes to a proxy server, and the
proxy server makes the request to the web server.
A proxy server can improve performance for groups of
users because it cache the results of all requests for a
certain amount of time. If a user requests a web page that
it already fetched for another user, it returns the page
instead of forwarding the request to the Web server, which
can be a time-consuming operation.
PUK (PIN Unblocking Key)
Security code that protects the phone/SIM against
unauthorized use. The PIN is supplied by the service
provider with the SIM card. It may be a four to eight-digit
number and can be changed, as required.
Roaming
Use of your phone when you are outside your home area
(when traveling for example).
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