The simple present is used for events that are not likely to change. For this reason, it is often used to state facts and habits. More specifically:
|Current habits||She plays tennis everyday.
My children go to sleep very early.
|Indicates state (used with stative verbs)||I know him.
I smell flowers.
|Indicates future (an adverbial is needed)||I have a doctor’s appointment on Wednesday.
I am working next Tuesday.
The simple past tense states facts, as well.
|Facts||I finally finished my book!
The Eagles won the game.
|Past habit||I watched that show every week.|
|An on-going past event which does not apply to the present||He taught English for 40 years. (He no longer teaches English.)
He lived in Florida for 15 years. (He no longer lives in Florida.)
|With stative verbs||He owed Nick money.|
The simple future cannot be used for facts because the future has not happened yet. Instead, the simple future is used for strong predictions (events that are very likely to occur).
|Action that will take place in the future||He will go to Paris next week.|
|Habit in the future||She will take the train every day after next week.|
The present progressive should be thought of as an event which is ongoing (unfinished) in the present. More specifically:
|An activity in progress||He is walking the dog.|
|An ongoing action that will soon end||I’m studying Literature.|
|A temporary situation||I’m living in Brussels right now. (I will probably move soon.)|
|Expresses the future (needs an adverbial)||She’s graduating university tomorrow.|
|A change in progress||She’s learning more every day.|
The past progressive should be thought of as an event that was ongoing in the past.
|An action in progress at a specific time in the past.||He was talking on the phone last night.|
|Simultaneous past action.||She was watching TV when the phone rang.|
|Repeated past action.||She was laughing during the entire movie.|
The future progressive should be used to describe an event that will be ongoing in the future.
|Action in progress in the future.||He will be swimming on the team for the next three years.|
|Duration of some specific future action.||She will be working for the news channel starting in April.|