.bz2 is a compressed file created with bzip2 utility in Linux. Extracting these type of files is straight-forward in Linux. Type the following command in Linux terminal:
$ bzip2 -d your-file.bz2
-d stands for decompress.
This will extract the file in same folder you are at the moment. To extract the contents to another folder, check this article: Extract .bz2 File to Another Directory in Linux .