: Extracting a single file from the middle of a solid archive is slower because the software must process all preceding data in that "solid piece" to reach the target.
The phrase appears to be a technical description of a compressed archive, specifically a "solid archive" created using the RAR format . Technical Breakdown CS.rar
: A solid archive is a special compression method that treats multiple files as a single, continuous data stream. Why use a "Solid" format? : Extracting a single file from the middle