When you make a reservation to invest, that company is currently in what we call the "Testing The Waters (TTW)" phase of their fundraise. This means they are taking pledges to gauge if they would have a successful raise. It is important to understand that reservations are non-binding and they do not guarantee anything such as getting in the fundraise, early bird terms, etc.
For a TTW fundraise, the invest page will initiate a Wefunder Cash transfer, drawing funds from an investor's saved bank or wire account or do a pre-authorization of your credit card. When the fundraise goes live, you will be asked to confirm the reservation and payment will be applied at that time.
Full scoop on reservations & Wefunder Cash here.