The table of contents of a disc is just that. It's a table of the disc's contents. There's no file for it on the disc, e.g. an excel file on the root with all the file locations in it.

In Swap Magic, it's important to know this because of the original game needing to have a higher TOC than the backup game.

Process:
Load Swap Magic
Eject normally and insert original disc <-- Must have a higher TOC than the backup disc below
Wait for SM to respond
Use swapping method and swap in backup <-- Must have a lower TOC than the original disc inserted previously
Load

This applies for both CD and DVD games.
You cannot use a single layer DVD game to boot a dual layer backup or vice versa. (as far as I know)

You can generally tell if a TOC is higher by doing a file count in explorer - i.e. put the disc in your Windows PC, open it in Explorer, highlight all the files and folders, right click and properties.

It's basically the same for Linux. Mac, I have no idea.
The number of files is the info you want. If the number of files on the original disc is higher than the number of files on the backup, that means the table, i.e. the list, of the contents of the disc would be longer and larger, so the backup will work.

There is a general correlation between disc size and TOC size, but don't rely on it - this method only takes a few mins more at max and is more reliable.

Fifa Street NTSC has one of the highest TOCs for a single layer game and is fairly widely available in NTSC countries. For PAL regions, go for Devil May Cry (the first one).