Modal verbs
Hypothetical possibility: would
Would is used to speculate and hypothesize
  about an unreal or improbable present or future situation.
  -   I would
    buy a new car, but I don't have any money.
-  I wouldn't go on a trip to the moon;  it's
    too dangerous.
-  Tell me, what would you do?
In positive sentences would is often contracted
  to 'd in spoken English.
  -   I'd
    come with you, but I'm busy.
- She'd do it for you, you know.