About Shopping Carts

Hello Group,

I'm currently working on a website through which I intend to sell a wide variety of health related products. I'm an experienced webmaster and I've built many sites in the past but the only way I've made money is through basic banner advertising via affiliate programs. Now I'm getting into shopping cart functions and developing an extensive surfer friendly catalogue of products.

I don't know if I'm posting in the right place, and if I'm not I'd appreciate if you could point me in the right direction, but basically I need to know how basic online retail businesses work. Ultimately I want to sell products without having to hold any inventory. I'm thinking how it will work is people will place orders via shopping cart and are charged with shipping & tax included and then I forward the orders along with the funds, minus my share, to the manufacturer who'll send it directly to the customers. I have no knowledge on how this is done but I'm sure it's a lot easier than I think it is.

Can any of you explain to me how this is done, or forward me to a website that explains it or has software for this?

I hope I made myself clear in what I'm looking for.
Looking forward to your responses,
Lee