A sales seat is an administrator or a salesperson, somebody who can change what the business sells and owes. A production seat is the shop floor, which reads the work and records what it has done. Seats of each kind get cheaper from the fourth.
Prices are in Canadian dollars. A US dollar price is not available yet, so your card is charged in Canadian dollars and your bank converts.
No card is taken and nothing is charged. You can move to a paid plan under Settings whenever you need orders, invoicing or more people, and a card is asked for then.