用户故事是从用户视角出发、用简洁日常语言描述的功能说明。它明确了谁需要什么、想要什么，以及为什么。验收标准定义了该故事的"完成"标准——必须满足的条件才能被接受。
标准格式
text
As a [type of user]
I want [some goal]
so that [some benefit].
Example:
As a returning customer
I want to save my shipping address
so that I don't re-enter it every order.
"为了"这部分最为重要——它表述了价值所在，帮助团队找到比字面要求更好的解决方案。
验收标准
text
Given a logged-in customer with a saved address
When they reach checkout
Then the saved address is pre-filled
And they can edit it before confirming
✓ Testable and unambiguous
✓ Defines done — no "I thought you meant..."