What is the difference between Salemaker and Specials? Both seem to be ways of reducing prices.

Salemaker is used to create a policy for reducing prices and then applying it to a group of (or all) products. You would use this to set up your 20% off January Sale for example.

Specials allow you to target price reductions at individual products. You might use this to reduce the prices of end-of-line products, while not touching the prices of new stock that you're bringing in to replace them.