Debit/Credit determines the normal type of transactions from the account. It is useful in Trial Balance filtering. It won't restrict the transaction to either credit or debit.
Another field that worth to mention is Account Type. You can create 5 types of G/L Accounts:
- Posting - posting transaction. All transaction entries are posted to this account
- Heading - heading description for a group of account. For description purposes only.
- Total - Totaling a series of account.
- Begin-Total - beginning of a series of accounts to be totalled.
- End-Total - Total for a series of accounts
If you want to post entries directly from journal lines, you must check the Direct Posting field. Of you totally don't want transaction to be posted to an account, then you can check on the Block field.