"sale" is a noun, and "sell" is a verb. For example,
They sell bread at the bakery.
The bakery sells bread.
The bakery near my house used to sell bread, but the store closed down. They sold the store, and now it is a pizza restaurant.
There is a sale on bread at that store. Bread is usually $3 a loaf, but today it is on sale for only $1 a loaf.
Hope that helps.