Pronouns are a kind of shortcut – language would be rather tedious without them. They are used in place of nouns or proper nouns – usually to avoid repetition. Often, a reference is made to a noun or proper noun directly, and then subsequent references to the person or thing are made using a pronoun. Examples of pronouns: him; her; it; his; their; you; them; me.
For example, to say ‘Johnny tried to put the frog in Johnny’s pocket, but the frog jumped out’ does not flow very well, so we use pronouns like this: ‘Johnny tried to put the frog in his pocket, but it jumped out’.
We will take a closer look at pronouns in Portuguese later, but for now it is enough to know basically what they are.