JPG files are always compressed, which means that as well as throwing away some information, they take up less space. RAW is effectively a direct sensor dump - nothing is thrown away or compressed (though some cameras offer a compressed RAW option).

JPG files use lossy compression, which means that as well as throwing away some information, they take up less space. RAW is effectively a direct sensor dump - nothing is thrown away or compressed (though some cameras offer a compressed RAW option).