Why must you use "this.characterName" in the constructor but do not have to use the "this" keyword in the return method?

In the video lesson on Java Objects we are shown two ways of making our code more understandable.

class PezDispenser{
  private String characterName;

  public PezDispenser(String characterName){

      this.characterName = characterName;
  }

  public String getCharacterName(){
    return characterName;
  }
}

and

class PezDispenser{
  private String mCharacterName;

  public PezDispenser(String characterName){

      mCharacterName = characterName;
  }

  public String getCharacterName(){
    return mCharacterName;
  }
}

The 'this" keyword is being used within the constructor to specify which "characterName" is being referred to. I assume that the "this" keyword does not need to be used within the get-method because it does not have access to the "characterName" being passed a paramter in the constructor? Therefor the only "characterName" it has access to is the class field "characterName?"

Thanks!

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