The application treats anywhere that money is kept as a bank account, so this could be a true bank or building society account, a credit card account, a petty cash tin, or a shop till, indeed you may have a number of tills set up as separate bank accounts.
Movements of money between these is processed via Bank Transfers, so that could be paying off the credit card from the bank current account, banking the day’s takings from the till, or cashing a cheque for the petty cash.
When receiving payments from customers, think carefully about which bank account this is being received into for example if they are paying electronically or by credit card, then it will likely go direct into your bank current account, but if paying by cash or cheque, it may all be going into a till initially, and then being banked later, so you will need to reflect that in your accounts by posting the payment received initially into your till (bank) account, and then making a Bank Transfer from till account to bank current account for the amount banked; if done properly, the amount showing in your till (bank) account should be the actual amount left in your till.
When making payments equal care should be taken in posting the payment to the correct bank account, for example payment made with a credit card will be taken from the credit card (bank) account, but payment made with a debit card will generally need to be posted as coming from the bank current account in the same way as cheques.
Payments made by cash would normally be posted as coming from the petty cash (bank) account, but in many small firms owners and directors often make payments out of their own pockets so you might want to set up a Director’s Loan (bank) account for anyone who does this on a regular basis, so that the payment can be posted as coming from that account, and the balance on the Director’s Loan (bank) account therefore represents the money owed to that individual (see also How do I claim Expenses? and When should I use Expense Claims rather than payments from a Director’s Loan account?).