When any type of element touches the edge is called a slug.// Usually non-printing Information such as a title and date used to identify a document.

it is the edge of where the page is going to be printed.//refers to graphics or design elements which extend beyond the print edge of your design piece. Bleed ensures that no unprinted edges occur in the final trimmed document.

it is like a margin.//it control the distances between page and layout elements, including single-column and multi-column text frames. Book designers set gutter to separate content on adjoining pages.

it is the space of the page you want like how long do you want you page to be basically the size.// mainly layout

Grids are lines in the background which would not be printed it is used to help you arrange thing properly.

a spine is the space between 2 pages so how long would it be.

How big the margin is mainly showed by 2 numbers blant times blank to know how long and wide it is.

Basically it is simple, it is how many pages are there in total in your document.