English is a complicated language.  It's rather annoyingly difficult in many respects, and somewhat simplified in others.  Many people have difficulty with English spelling.  The grammar has it's ups and downs, but here is some help.  This series is for those who would like to brush up on or learn about grammar and grammar terminology.

English has many more pronouns than those we refer to as Personal Pronouns.  Some of them border the line between pronoun and noun.  Now let us look at some of these funny little pieces of our grammar.

First we have demonstrative pronouns. These are seperated by time and space.  Closer and always present things use This and These.  Farther things or past things use That and Those.
The chart looks like:

We can use them as adjectives (or some consider them Determiners like the articles), but by themselves they become pronouns.  Sentences like "This is a good book," or "These are great pants,"  or "That's okay."

We also have the Relative pronouns.  These usually start a relative clause.  In sentences like, "That man, whom I saw running, was shot."  Whom is a relative pronoun in that case, refering back to the noun man.  These always begin what we call a dependent or embedded clause.  Some of the pronouns in this category are who, whom, whoever, whomever, which, whichever, that, amongst a few others.