Direct Lender and Mortgage broker

[Akash Sky]

Hello!  

I've been doing some googling to try and figure out what the difference between a direct lender and a mortgage broker is.  So far, I've only discovered that "Direct Lenders" can be cheaper than "Mortgage Brokers" because the mortgage brokers charge you a commission in addition to the lending fees.  

Other than that, I really don't understand the difference.  Also, if I go to a bank, how can I tell whether or not they are going to act as a direct lender or a mortgage broker?