Direct Connect is used to download transactions directly from your financial institution into financial software account registers. Direct Connect is an automated process that either happens when you first use your software for the day or when you click on a button or feature link to start the download process.
Direct Connect usually uses the OFX protocol, which allows the software to communicate with an online banking site. With Direct Connect, potential duplicate transactions are filtered out (if the transaction is already entered in the register, it's not downloaded again) and only new transactions make it into the register.
Another way to download transactions into financial software is via WebConnect, which differs from Direct Connect in that the financial software user must export and download transactions from each FI's online banking site individually and then import the transactions into the software.