A BZIP2 file refers to content minimized using the bzip2 format, most often ending in `.bz2` or appearing as `.tar.bz2` when many files were tarred first, extractable through 7-Zip, WinRAR, or commands like `bunzip2` and `tar -xjf`; bzip2 favors text because it processes blocks through Burrows–Wheeler to cluster symbols, applies Move-to-Front to make them numeric and small, and then run-length encodes those recurring values.

Finally, bzip2 performs Huffman symbol coding so common symbols get very short codes, achieving major compression benefits after BWT+MTF cluster repetition, making bzip2 strong on text but slower and more memory-heavy than gzip; `.bz2` typically decompresses into one file, while `.tar.bz2` indicates a tar archive compressed afterward, requiring two steps unless the tool handles both automatically.

That’s why extracting a `.tar.bz2` can show a `.tar` stage: bzip2 removes the compression, leaving a `.tar`, and then the tar archive unpacks into the file tree, though tools like `tar -xjf` streamline both; the extension effectively signals whether it’s a single-file `.bz2` or a compressed tar archive, and decompression is the key step—`.bz2` restores one file, while `.tar.bz2` expands into multiple items, with bzip2 also suitable for creating compact archives except when handling data like JPG or ZIP which already compress poorly.

What you can do with a BZIP2 file varies by how you intend to use it, but usually you begin by decompressing since `.bz2` isn’t directly usable; a `.bz2` expands to one file that you open in its native app, while a `.tar.bz2` unpacks entire folder trees for software installs or project recovery, and you can also create `.bz2` archives to save space on large text files, swap compression types to shrink tarballs further, or rely on `.bz2` in automated systems where logs and data dumps are stored compressed until needed.

To open or extract a BZIP2 file smoothly, you first tell whether it’s a simple .bz2 or a tar-based .tar.bz2, because `.bz2` restores one file while `.tar.bz2` expands into a directory via an intermediate `.tar`; Windows users often use 7-Zip/WinRAR, macOS/Linux users rely on `bunzip2` or `tar -xjf` (with keep options for preserving `.bz2`), and mobile devices need archive apps, with the most common confusion coming from tarballs behaving differently from ZIPs, auto-deletion of compressed files, and extraction errors due to corrupted or misnamed downloads.

To open or extract a BZIP2 file, the first task is to decompress the archive, meaning `.bz2` expands into one file you then open normally and `.tar.bz2` expands into a `.tar` that in turn unpacks into its folders, though command-line tools can do both steps together; be aware of utilities that delete the source `.bz2` automatically and of extraction errors that typically signal corruption or misnamed data, with alternate extractors like 7-Zip helping diagnose the problem.