Would is a modal auxiliary verb.
Would is used as a softer less definite form of will, in some cases as past of will.
1). In indirect speech, would is used after past reporting verbs where will was used in direct speech.
Tomorrow will be fine - DIRECT
The forcast said the next day would be fine - INDIRECT
2). Future in past tense - Would is used to express the idea of "future in the past" - to talk about a past action which had not yet happened at the time we are talking about.
In Berlin, he first met the woman he would one day marry.
There was a chance that my letter would arrive in time.
3). Would is used in polite requests and offers as a softer form of will.
Would you open the window, please?
If you would come this way.....
4). Would can refer to past willingness of a general kind, but not to willingness to do something on a particular past occassion.
She would hoover, dust and iron, but she didn't like doing windows.
She agreed to come and see me . (NOT - She would come and see me)
But would not can be used to refer to a refusal on a particular past occassion.
I asked her very politely, but she wouldn't tell me.
5). Conditional auxiliary: I would....if - Would is often used as an auxiliary with verbs that refer to unnreal or uncertain situations - for example in sentences with if.
I would tell you if I knew.
It would have been nice if he'd thanked you.
6). Typical behaviour - Would is used as the past of will to talk about typical behaviour in the past.
When she was old, she would sit in the corner talking to herself for hours.
Sentences with stressed would can be used to criticise people's behaviour.
He was a nice boy, but he would talk about himself all the time.
Stressed would can also be used to criticise a single past action - the meaning is ' that's typical of you '
You would tell Sania about the party - I didn't want to invite her.