Your customers can pay either using a credit card or issuing them an invoice.
If the credit card option is chosen, your client will be charged during the booking process and you will immediately get the money on your Stripe account.
If payment is to be made by invoice, the customer will receive an invoice indicating the amount that is owed and will need to be transferred to your bank account within 7 days. PayPal payments will be available as an option soon too. As an expert, you can specify in your dashboard which payment methods your customers should be able to make.