What is the difference between concepts and descriptions and when to use each?

I mean, how do they affect your cards? What is the difference between a card I made as description and as concept. Like if I make card commutative property of addition :: a+b=b+a vs Commutative property of addition :: a+b=b+a, what would be the difference between card? And when should you use one vs the other?

The documentation has all the answers, but in short: concepts are used to create both forwards and backwards cards and don’t show their parents when references; descriptors have a forward card and a card that asks for their parent and show that parent when referenced.

In your example, you would use a concept if you wanted to test yourself on what property is symbolically represented by a+b=b+a (which would be the backward card), and you would use a descriptor and remove the “addition” from the forward part to test yourself on which operation’s commutativity is commonly represented with a plus sign. Their forward cards would be the same (except for the removal of “addition”).