Could you please help me to understand the difference between 負担｛ふたん｝ and ロイヤルティ?
ロイヤルティ is royalty, the money that must be paid typically to a patent owner, a copyright holder, etc. This is a pure technical term, so see the English Wikipedia article for details.
負担 is much more common, and in financial contexts it refers to a share of money you have to pay (for whatever purpose). 負担 also means workload, (psychological) burden, etc.
- 税金の負担 tax burden