Have you ever thought that your use of pronouns might reflect your level of self-esteem and whether you belong or fit in a group? Here is a link to a review of James Pennebaker's "The Secret Life of Pronouns." It came from brainpickings.org, which is a site you might want to subscribe to. (I think the name of the site captures the essence of it.)
I often start my ESOL classes with a brief review of the eight parts of speech. I am always amazed at how few students understand that our language and dictionaries are made up of words that belong to certain categories of speech. Why do we do that? It is so we can know how to use the vocabulary in a sentence.
What is a pronoun? Simply defined, it is a word that takes the place of a noun (=a word that refers to a person, place, thing, or idea). However, in English, we should not use a pronoun in a sentence unless it is obvious to the reader or listener what noun you are referring to. Here are some examples:
"She loves to travel overseas."
If you had been talking about Maria previously and said the sentence above, I would assume that you were referring to Maria (="She").
Some languages such as Japanese and Spanish don't require a subject (often played by a noun or pronoun) to start a sentence, so you definitely need to be following the conversation or reading well to understand the subject of a statement.
"Es muy interesante." what or who is interesting?
Pronouns are useful, especially to allow us to avoid repeating the same noun: "When John was at the zoo yesterday, John saw a giraffe." Better and easier to follow would be to say "When John was at the zoo yesterday, he saw a giraffe."
For more in-depth coverage of Dr. Pennebaker's fascinating perspective on human social interaction and what language tells about our state of being, I recommend this recent 2017 Apple interview. It will also connect to education and English language learning.