: Right-click and select "Add to archive..." .
: If one part of the archive is damaged, it is much harder to recover the files that come after the damage in the data stream. Also, updating a single file within a solid archive is slower because the whole stream must be re-processed.
In the world of compression, a "solid" archive treats multiple files as one continuous data stream, which usually results in much better compression ratios, especially for many similar files.
: It’s great for sets of similar files (like a collection of documents or log files).