Here are some proper nouns:
Saturday, Mrs Key, Father Christmas.
...and some common nouns:
camera, chair, picture, book
Pronouns are used instead of nouns, for example:
Mrs Key took a photo with her camera. Mrs Key was very pleased with her photo.
We could replace some of the nouns to make the sentences sound better:
Mrs Key took a photo with her camera. She was very pleased with it.
We practised replacing nouns with pronouns and there were a couple of learning points which arose:
Don't be afraid to replace more than one word with a single pronoun. For example, 'Rob's large painting' could be replaced with 'it'.
Pronouns which replace proper nouns don't have capital letters except for 'I'. Of course, they may need a capital letter because they are at the beginning of a sentence.