It expresses an offer or invitation. Example : Would you like a cup of coffee? or Would you like to come to birthday party tomorrow?
It expresses what one wants politely. Example : I'd like a room, please.
It expresses the result of condition in a contrary-to-fact situation. ( Conditional Sentences Type II) Example : If I were rich, I would buy you a house. It means I'm not rich, so I will not buy you a house.
It expresses the result of condition in a contrary-to-fact situation in the past ( Conditional Sentences Type III). Example : If she had driven the car more slowly, she wouldn't have had an accident. It means she didn't drive the car slowly so she had an accident.
It expresses polite request. Example : Would you be kind to type a letter for me?
It expresses a habitual action in the past. Example : When I was young, I would play game online for hours.