Marketpace is like a store for your vanilla site. It is deployed in plugin form but is more of an app in its own right.
It currently support three payment gateways Karma and two real money gateways, PayPal and Stripe. The latter allows you to take card payment on your site.
It is recommended that you use ssl if you are taking card payment directly. You can use the force SSL to redirect to the https:// address.
The currencies supported ore the currencies supported by the individual payment gateways. So PayPal is suitable for international payments. Stripe is USD only an you need a US bank account receive.
It does NOT come with an integrated cart, or extensive merchant service. However it is a way to economize your site.
It comes with store and item pages, which you can customise the urls.
Product Types are proto product plugin, which determines what a product does. It could be anything from getting invites, to a premium role, to buying karma. Effectively the payload or callback operation.
Product Type plugins are prefixed with 'Purchase'. They are separate plugins. Search for them.
At the moment there are no manual Product Types.
Marketplace comes complete with a transaction log which you can query an filter.