Very easy to remember
The first thing to know is, what is concrete? Here’s the difference.
Concrete has stones in it and is used for thick jobs like sidewalks and foundations and it adds more strength.
Mortar is concrete, but without the stone. You would use mortar for patching or applying a stucco finish on a foundation wall. Or other similar repairs.
Both have sand and lime in them. The sand helps to make it stronger. The lime is the hardener used in both concrete and mortar.