A person who is a Nobleman is someone who belongs to Nobility. Nobility is a social class consisting of people that have more privileges than the other classes in the society.
Regarding your question about the difference between people, person, animal and thing, I hope the examples below help you.
The boy and the girl were found tied to the pole in the warehouse.
The participants have been shortlisted for the quiz.
Each student is entitled to five minutes of rest time in between the four-hour examination session
Rahul is a bright child.
Shweta won three golds and two silvers for her school.
Mr Anand is our Geography teacher.
An elephant is a huge mammal, but not as huge as the whale.
The bullocks were Ramu's only help in his fields.
The camels and the giraffes were thrown into a small enclosure in the zoo.
All the tables are full.
The jar is full of ice-cold water.
I know an old man who can turn dust into gold.