Credit-card processing

All the basics of e-commerce, in this thread

[anshul]

I wanted to know details about credit card processing.

How're credit cards processed, validated and (automatically) charged amounts from customers?

What are payment gateways? Verisign?
Why such gateways and SSL costly?

Is PayPal a payment gateway?

Do we've these thing already in an e-cart like OScommerce or cubecart or zencart?

I'm a stupid about that. I request a fine discussion on this topic.

[BeeDeeDubbleU]

I am sure that this has all been covered before. does anyone know of any previous posts that provide a full intro to ecommerce?