Here are the few naming conventions that are followed since 1.7.0 version. 

Previously,
In Woo discount rules --> Price Rules Settings --> Discount tab. 


From 1.7.0 it is, 



All selected is henceforth Auto add all selected products
Same product
is the same.
Any one cheapest from selected is the same.
Any one cheapest from all products is the same.
More than one cheapest from Selected Category is henceforth Cheapest in cart - selected category(ies)
More than one cheapest from all selected is henceforth Cheapest in cart - selected item(s)
More than one cheapest from all is henceforth Cheapest among all items in cart.


A one line definition on each of the discount type:
Auto add all selected products:
The mentioned products will be automatically added to the cart.

Same product:
Get discount in same product.

Any one cheapest from selected:
 Get discount in one selected product.

Any one cheapest from all products:
One cheapest product from cart will be discounted.

Cheapest in cart - selected category(ies):
 Cheapest product from the selected category will be discounted.

Cheapest in cart - selected item(s):
Get discount in chosen no.of quantities.

Cheapest among all items in cart:
The cheapest product from cart will be discounted.

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