I am confused about 'committed transactions' in the transaction log. I was reading that when you backup a database it only takes the committed transactions. But I also read that when you perform a transaction it writes it to the transaction log but does not committ to the database until a checkpoint. However if i were to make a change to a users account and check the database I see the change. I dont understand what it means by it doesnt write to the database until it is committed. Also when does it committ?