Basic question

Hi Friends,

I know this is a pretty silly question to ask. Could you please helo me understand what a Debit and Credit means in SAP accounting?

Also, what is a cost of sale? What are the accounts that are hit when we procure goods to stock and when we directly ship goods to customers from vendors.

1) An invoice is raised.

2) A goods is receipted

3) An invoice is receipted.

Appreciate if any one can help me with a link that can help me understand the basi