Hello. Please could somebody explain exactly what 'compact file' does [other than "tidy up the file" or "minimise crashes"].

I like to feel like I'm in control of the data and know what is happening to it [because, even with constant backing up, an introduced problem probably wouldn't be immediately apparent]. Does 'compact file', for instance, do something like this: Census sources for one household but each household member has their own source citation - does 'compact file' group all the household members together for one source citation? Is it something like that?