Package Managers keep track of installed software as well as dependencies (i.e., if a particular software needs certain libraries installed in order to function properly, a package manager would notify you and install the other required software or dependencies).  Most Linux distributions fall into the category of using rpm (originally known as “Red Hat Package Manager” but now known as the recursive “RPM Package Manager”) or dpkg (“Debian Package Management”).

For rpm, the software to be installed is bundled as an .rpm file.  I think that the .rpm file is a special binary file, so you need to use the rpm command to see the .rpm file contents.  Use rpm -qip filename.rpm to see information about the package and rpm -qlp filename.rpm to list the files that will be installed. RPM is used by Red Hat, Fedora, CentOS, SUSE, and openSUSE, to name a few.  It is important to note, though, that some distributions have more user-friendly rpm tools — for example, on SuSE and openSUSE, YaST2 (Yet another Setup Tool) is used.

For dpkg, the software package is contained in a .deb file. The .deb file is actually an ar archive (not to be confused with “tar” archive). You can use dpkg -I filename.deb to see information about the package and use dpkg -c filename.deb to list the file contents. Alternatively, you can use the ar command to extract its contents, which consist of “control” and “data” compressed tar archives; many graphical archivers can also open up the .deb file for you.  dpkg is used by Debian, Ubuntu, and KNOPPIX (basically, any distribution like Ubuntu and KNOPPIX that are based on Debian would use dpkg).  Except for software not included in the repositories, one would typically use apt instead of dpkg to install software — for example, use apt-cache search program to search for the package name of “program” in the repository, use apt-get install package to install that “package”, and apt-get remove package to uninstall the “package.” Graphical installers are available as well.

What happens if you’re using a Linux distribution that uses dpkg but you get an .rpm file, or vice versa?  alien is a handy way of converting between .rpm and .deb package formats.

ANSYS software (ANSYS, Workbench, CFX, FLUENT, Polyflow, AUTODYN, etc.) doesn’t use package managers, so the installation script will install ANSYS software for you regardless of which distribution you use.  Hence, you don’t have to worry about packages, but you do have to check that you have required dependencies yourself (see the Installation and Configuration Guide in the ANSYS documentation to see what packages may be required).
(Note that Ansoft software does check the operating system, so you can’t use the installation script without using a supported distribution for Ansoft products.)

There are some other commercial packages that may use package managers to distribute their software.  If I remember correctly, the older Intel Fortran compilers for Linux used rpm, although the current version (11.1) seems to support Ubuntu (.deb).  If you get software that is only in a package manager format you don’t use, try alien to convert the package file.