Contiguous simply means touching or sharing a border, according to Merriam-Webster. When it comes to the United States, contiguous refers to all of the states that touch one another, without another country or a body of water coming between them. These are sometimes also referred to as the lower 48 states.
.apk extension stands for android package file. It is a file format used to distribute and install applications.It includes the programm codes ,assets ,resourses ,certificates and manifest file. .Dex extensions stands for Dalvix Executable files.
An APK is the Android equivalent to an .exe program on your computer. Instead of downloading an app from the Play Store, you simply install it yourself without the Play Store's help (see our guide on installing apps outside of Google Play.