Kadalai paruppu refers to groundnut (peanut) in Tamil. It is the whole, dried peanut, sometimes called peanuts in the shell.
Pottu is a powder made from roasted and ground lentils, typically black lentils (urad dal). It is often used as a decorative mark on the forehead in some cultures.
Here's a summary:
* Kadalai paruppu: Whole peanuts
* Pottu: Powder made from roasted and ground lentils
While both are legumes, they are different types of legumes and used for different purposes.