Are these referring to the same words? I see them used around interchangebly. Also for the rest of the pronoun types eg: - I believe the following are synonyms too: "Subjective Pronouns" "Subject Pronouns" "Personal Subject Pronouns" etc. How is one supposed to be great in grammar when the structure is so loose?
Not all pronouns are personal pronouns.
I recently looked through the Cambridge Grammar of the English Language and from what what I remember, it uses the term "personal pronouns" to refer to not only the "core" pronouns "I, we, you, he, she, it, they" but also "one" and "there" (see the explanation mentioned in Elise Mignot's paper "Pragmatic and stylistic uses of personal pronoun one"; basically, the authors seem to use "can it appear in a tag question" as the main criterion).
The word who is an example of a pronoun that is not a personal pronoun. Who is classified either as an interrogative pronoun or as a relative pronoun, depending on the context and usage. (I still haven't learned all the criteria for distinguishing between these two uses of who).
Subjective, subject, objective, object
"Subjective"/"Subject" and "Objective"/"Object" are examples of variable terminology. The problem is that English does not really have a systematic distinction between one morphological case typically used for subjects and another morphological case typically used for objects in the way languages like German, Russian or Latin do.
In English, there are only six pairs of distinct "subjective" and "objective" forms—I/me, we/us, he/him, she/her, they/them, and to a lesser extent who/whom—and you can see that for about half of these, the two forms don't even have any clear resemblance to one another.
Because the phenomenon of English pronominal "case" is so different from the prototypical examples from other languages of a nominative case/accusative case distinction, some people don't like to use the terms "nominative" and "accusative" when talking about English grammar.
Some people think that the terms "subjective" and "objective" are a less misleading way to describe the distinction between different types of pronouns in English. (The Wikipedia article on "Nominative Case" says "The English language is now often described as having a subjective case instead of a nominative, to draw attention to the differences between the "standard" generic nominative and the way it is used in English.")
"Subject pronoun" and "object pronoun" are just variant terms.
There are a number of contexts where me, us, him, her, them behave differently from whom. Most obviously, a "personal objective pronoun" form must be used if the pronoun is (by itself) the direct object of a verb ( *"They helped I" is not grammatical; it has to be "They helped me"), whereas the form whom is optional as the direct object of a verb ("Who did they help?" is grammatical; "Whom did they help?" is not required).
Another difference is that it is ungrammatical to use whom as the predicative complement of a finite copular verb (*"Whom was it?") whereas it is grammatical to use me, us, him, her, them predicatively ("It was me").
In my opinion, calling them subjective or objective pronouns amounts to conflating the terminology with subjective or objective case. In any event, "subjective" and "subject" would be used synonymously here, and likewise for "objective" and "object".
I would have thought that personal pronouns are a subset of all pronouns, including I, me, you, he, him, she, her, we, us, they, them, who, anyone, somebody, while impersonal pronouns include it, what, something. However, all the usage notes I can find indicate that personal pronouns are those that stand in for "grammatical persons" (I, you, him, she, they, them)--as in first person singular, third person plural, etc.--while impersonal pronouns are like "one".