How does the trade customer discount feature work?

When adding/editing a trade account, at the very bottom of the page you are asked the '% discount on normal pricing'.

This is where you can specify a percentage discount that the trade account will get on the normal product price.

For example, if a product's price is £100.00 and the trade account has a discount of 10%, then if the trade account is logged into their account they will see the product price as £90.00

If you don't want the discount to be applied to certain products, when adding/editing the product scroll to the 'additional information' box and tick the 'is this excluded from trade discounts?' tick box.