What is Tadka Bhagar Tempering or Phodani?

All these terms mean same. It is a method of adding spices, specially: mustard seeds, cumin seeds, coriander, and Asafetida (Hing).

A contraption called 'Pali' is used. Pali is a long handle crucible made out of either iron, copper or brass alloy. The crucible can hold about six ounce of fluid. A small amount of cooking oil is placed in the crucible and heat. The spices are added to hot oil and heat more. The process releases volatile oils from the spices. While still hot, the contents of Pali are dumped into the curries to add aroma, specially when Dal is made. The process allows to disperse oil soluble flavor throughout the curry.

One should not use Ghee or Butter for Tadka. Recent studies have indicated that it could create cancer causing hydrocarbons. You should use oils. It will take practice, you do not want to burn oil, or the spices.