a note is an agreement to make payments. It is like an IOU, but with lots of fancy terms. For example if I buy your house and you agree to let me owe you $10,000 of your equity paid for 5 years of interest only payments of $100 and then a baloon payment of $10,000 at the end. That would be an interest only note with a baloon payment.

Real estate note means you are financing the purchase of real estate by promising to pay.

A mortgage is something you give back to the note holder. It means you are putting up the property you bought as collateral for the note. If you don’t pay then they can foreclose. It is a special word because kicking someone out of a house is a big deal and they needed to make special laws for it hence its own word. You will never have a real estate note without having a mortgage. There is no reason not to have to collateral.

deed of trust is better than a mortgage if you are the lender. It has a third party involved that holds the title until the note is paid off and allows for quicker foreclosure if you don’t pay.

business note is a note to buy a business

commercial note is a not to buy wheels for your car, a car, skis, etc

note sale means you are selling a note. Lets say someone owes you $100 interest payments only, on a $10,000 note with a baloon payment at the end of 5 years. They owe you a total of $6,000 interest and $10,000 at the end. After they pay you for a year you decide to sell it. You can sell that for something less than $14,800 if you want (no one would pay you the full value to wait for the money for no reason). You would have to do a lot of math to see what it would sell for based on what interest rate someone would need to take the risk that the person may not keep paying.
References :
http://homebuying.about.com/cs/realestateglossary/g/deedoftrust.htm