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.
As is the case with many file formats, APK files can have any name needed, provided that the file name ends in .apk. APK files are ZIP file formatted packages based on the JAR file format, with .apk file extensions. The MIME type associated with APK files is application/vnd.android.package-archive.