We can use the past simple to talk about actions and states which we see as completed in the past.
- I left school when I was sixteen.
- I was very happy then.
- He told me all about his childhood.
We can use the past continuous to talk about past events which went on for a period of time.
- While I was driving home, Peter was trying desperately to contact me.
- I was thinking about him last night.
- I was walking in the street when I suddenly fell over.
We can use the present perfect when we want to look back from the present to the past.
- I've broken my watch so I don't know what time it is.
- She hasn't arrived yet.
- We've been to Singapore a lot over the last few years.
- Have you ever been to Argentina?
The Present Perfect Continuous can be used to talk about an action or actions that started in the past and continued until recently or that continue into the future.
- You look tired. Have you been sleeping properly?
- I've been waiting for him for 30 minutes and he still hasn't arrived.
- He's been phoning me all week for an answer.
