Can my users use credit card to pay for things?

Your customers can use any WooCommerce gateway they want to pay for things.

What is stripe for then?

Stripe is a payment gateway. If you use the Stripe gateway purchased @ wcvendors.com > our plugins > stripe then you can also use it to instantly pay vendors their commissions, too.

More info.

https://docs.woothemes.com/document/stripe/

That gateway will work to collect money from customers using Stripe, but it does not have the capabilities to *pay* vendors commissions instantly. The wcvendors.com > our plugins > stripe would be the only version that has the code for that built into it. If you dont have the desire to pay vendors using Stripe, then any stripe gateway would work just fine.