deb is the extension of the Debian software package format and the most often used name for such binary packages. Debian packages are standard Unix ar archives that include two gzipped, bzipped or lzmaed tar archives: one that holds the control information and another that contains the data. The accepted program for handling these packages is dpkg, commonly used via other programs such as apt/aptitude or Gdebi.
RPM Package Manager (RPM) is a package management system. The name RPM variously refers to the .rpm file format, files in this format, software packaged in such files, and the package manager itself. RPM was intended primarily for GNU/Linux distributions; the file format is the baseline package format of the Linux Standard Base.
If you can only find some software you want to install in one of these package types but you need the other, this article tells you what to do. Note we are just passing along the link, and do not guarantee that this will work:
How to convert from .deb to .rpm and viceversa (Linuxaria)