A cultivar name almost always refers to one plant and its clones. So what is a plant clone?
The closest analogy to “plant clone” I can think of is “identical twin”. You probably know that identical twins are genetically identical. They look exactly the same because the instructions for how their body was built is the same.
If you make a new plant from leaf, stem, rhizome cutting ect, then the new plant is genetically identical to the original. People call this way of making new plants “vegetative propagation”. It makes clones! If you ask for a plant by its cultivar name you are asking for an identical twin of the original plant.