1. willingness, choice, acceptance (in a past context):
Ex : The test monkeys wouldn't wear certain perfumes. The test monkeys were not willing to wear certain perfumes.
2. desire, potential, after the verb to wish:
Ex : I wish this new product would be successful. I really want this new product to be successful.
3. an action in the past, with the emphasis on repetition or obstinacy:
Ex : My father would always take me to the zoo. My father always used to take me to the zoo.