This is a practical oversimplification which will be right most of the time. For more detailed information see Mastery of the Tenses!
For repeated actions and habits in the past. Often in stories.
- When I got home my mum would always make me tea.
- He would always do his homework at the last possible moment.
- They would come to our house at Christmas.
- She would smoke 60 cigarettes a day!
Used in the Consequence clause when it is improbable or impossible. NOT IF CLAUSE (generally).
In Second Conditional sentences
- If I were you, I would go.
- If she was nice, she would invite us.
- They would be so excited if they won!
In Mixed Conditional sentences
- I would be so happy if she hadn't done that yesterday.
- We would all speak English, if we had studied harder.
- They wouldn't be here, if we hadn't invited them.