<<If people buy from different buyers then how does a cart work? It works on other sites as they
are buying from the same business.>>
Hmmm, well buying from buyers is only feasible if the buyer is selling at the time, making that
vendor, however temporarily, a seller not a buyer for the purposes of the transaction. (heh)
On a serious note, - the way the cart works (for those who have it) is when viewing a listing there
is the Buy It Now button and right under that is a similar looking button for Add to cart.
When you add items to the cart, you can shop around at leisure, adding stuff from assorted sellers,
and when you are done, you simply go to the checkout and all those items in a same currency can be
paid at once.
Sellers offering combined rates for purchases of multiples should have it set up so that the discount
is applied at checkout. If it is not there, hold off and first contact the seller.
You are not 'committed' to pay for items in your cart. However, those listings have not been removed,
meaning someone else can click Buy on the listing, pay for it, and it vanishes from your cart because
she paid first.
Which is only fair, when you think about it.
So if you find something that is such an outrageously great deal that you simply have to have it,
it is wise to pay right away, and then continue your idle shopping - to ensure you don't lose out.
If you click Buy It Now, you next see a screen asking you to Commit to Buy, and if you make the
second click it puts the item in your Purchase History and you will be expected to pay for it.
You have, after all, 'committed' to pay for it.
If you simply want to browse, below the Buy and Cart buttons is the phrase Add to watch list.
By clicking that, you add items to a personal Watch List that you can ogle all you want without
ever having to make a decision.
These items, too, can be grabbed up by other buyers, -- and usually are.
Happy shopping 
