The Media Table is a list of all the file dependencies of the current document.
You can find the name of the file, its codec, width and height, lenght and time base if it has some, size and instances.
You can also click the
button on top.
If you right click on a file, you can preview it, reveal its location in your explorer or media directory, select it, update it, or create a new Compo from it (separate from the current document).