KisMetParty

File extension RAR stands for Roshal Archiver. In the same way PK in PKZip stands for Phil Katz. Storing information in a way we see it (words, paragraphs, pages) is very space inefficient. That is why computer scientists invented lots of multiple ways to compress the information. It is actually quite simple to understand who basic principle of compression works. For example if you have document which consists mostly of words "dog" and "cat" you can replace "dog" with "*" and "cat" with "+". Thus "dog chases cat" would look like "* chases +".

File extension DAT stands for DATA. This file extension is used by huge number of applications to store different helpful textual and binary information. Files with DAT extension usually tends to be quite huge.

If you have problems with any of the format above try finding an application which corresponds to your format.

Also I'd like to cover one bonus file extension since it became very popular in the age of internet. It is file extension XPI. This extension is used by Mozilla Firefox for installing Firefox extensions over the internet.

File extension BIN stands for BINARY. Binary is a way of representing information in a way which computer could more easily understand. You probably heard that computer doesn't count in a way we do from 1 to 10 but does it in a different way using binary systems where there only 2 digits - 0 and 1. So number 2 will be codes as 10, 7 as 111. So BIN files are usually used to store information coded in binary form which application could use during its work.