A discount is a price reduction.
It's often expressed as a percentage. You can get a discount on goods if they're faulty or late, for example, or simply because you're a good customer. If a supplier wants to get rid of some stock quickly, they may decide to sell them at a discount.
A sale is an event.
This often happens at a particular time of year. For example, at the end of the summer or winter season, many retail outlets have sales during which goods are sold at a reduced price. Sales are temporary.
Your phrase 'discounting market' doesn't really make sense. If you bought it at an outdoor/indoor market, you could say maybe 'a discount stall in a market', or if it's from a shop/store, you could say 'discount store'. These are places which sell goods at discounted prices all year round.
I hope that helps.