Marketing and loyalty
Create promo codes
Percent, amount, free shipping, buy X get Y, tiers.
In Orders → Discounts, create a code and pick its type.
Add conditions if needed: minimum amount, first order, eligible products, dates.
"Buy X get Y" gives the cheapest items free; tiers raise the discount with the cart.
At checkout, the customer sees why a code doesn't apply (minimum amount, expired…).