There are two giants who rule over the world of credit and debit cards, Visa and master card.

Almost every credit card, almost every debit card that people have in their pockets.

Almost certainly, they are from the thousands of banks that are aligned with Visa and MasterCard.

That's our colleague Anna Maria Andriotis.

She says Visa and MasterCard run the biggest payment networks in the US.

That's the infrastructure that many card transactions depend on.

Think of it as a set of rails.

If those rails aren't there, the train can't move. If you, the consumer, go to pay with

your credit or debit card and there is no network tied to that card, no network

enabled on that card, your transaction is going nowhere.

You are unable to make that purchase.

Banks rely on these networks for their cards, but some have their own networks, like Discover. Discover's network is pretty small. It only

accounted for 2% of the $10 trillion in US credit and debit card purchases last year,

according to the Nilsen report.

Discover a competitor or at least supposed to be a competitor.

Transaction volume that went over its network rails compared to Visa and MasterCard

was kind of laughable.

It was basically a rounding error.

For years, Anna Maria has thought that someday someone would try to challenge Visa and Mastercard by buying Discover.

And then on Monday...

A major credit card company will soon have a new owner.

Capital One will purchase Discover Financial for $35 billion,

...