The file name ending in indicates this is a multi-part (split) archive .
Large files (like software installers, high-quality videos, or sound libraries) are often split into smaller "volumes" to make them easier to download or share.
The downside is that to extract even one small file from the end of the archive, the software must process all previous data in the "solid" block first.
Programs often use multi-part RARs for extraction to a temporary directory before installation.
If one part of a solid archive is corrupted, it is much harder to recover the remaining files compared to a non-solid archive. What "part1.rar" Means
To extract the contents, you must have (e.g., part1, part2, part3) in the same folder. Opening just the first part usually allows you to begin the extraction process for the entire set. Likely Contents