Theory:

A proper noun is a name given to something to make it more specific.
Example:
Naresh
Lake Eerie
Ferrari
Monday
Mona Lisa
The Pacific Ocean
Important!
The” is a pointing word, and with a proper noun, the word has already been made specific, and there is no need to point.
Proper nouns in sentences:
Example:
1. Those people have been annoying Jamila.
2. Can we visit Tajmahal?
3. Charminar is located in Hyderabad.
However, there are times when a word can be used as either a common noun or proper noun and you might get confused as to when you should use the capitalized form. For example, “dad” can either be a common noun or proper noun.
 
One rule for thumb is that if you are using the word as a title and name it should be capitalized.
 
1. I had dinner with my dad last night.”
2. “Would you like to have dinner with me, Dad?”
In the first example, the word "dad" was used more generally as a common noun. In the second example, the word "dad" was used as a name. In this instance, the term “Dad” took the place of the actual name, such as "Madhav".