The .rar extension indicates a compressed folder. The part19 means this is the 19th segment of a larger set. You usually need all parts (part1, part2, etc.) in the same folder to successfully extract the contents.
Ensure the site providing the link is reputable. Download MP3 001 part19 rar
Sometimes malware is disguised as multi-part archives. Ensure your antivirus is active before opening. Download MP3 001 part19 rar
Without parts 1 through 18, you won't be able to open or listen to whatever is inside "part19." Download MP3 001 part19 rar