翻译自：https://developer.apple.com/library/ios/referencelibrary/GettingStarted/RoadMapiOS/AppDevelopmentProcess.html#//apple_ref/doc/uid/TP40011343-CH4-SW1
Ask yourself these questions as your define your concept:
Who is your audience? Your app content and experience will differ depending on whether you’re writing a children’s
game, a to-do list app, or simply a test app for your own learning.
What is the purpose of your app? An app needs a clearly defined purpose. Part of defining
the purpose is understanding what one thing will motivate users to use your app.
What problem is your app trying to solve? A great app solves a single, well-defined problem
instead of attempting solutions to multiple distinct problems. For example, the Settings app allows users to adjust all of the settings on their device. It provides a single interface for users to accomplish a related set of tasks. If your app is trying to
solve unrelated problems, consider writing multiple apps.
What content will your app incorporate? Consider what type of content your app will present
to users and how they’ll interact with it. Design the user interface to complement the type of content that’s presented in the app.
在定义app概念的阶段，回答自己以下问题：
谁是你的app的用户? 给不同用户写的app，体验和内容是不同的。给小朋友写的游戏，给大人用的Todolist应用，或是给自己学习app开发用的测试应用，内容和体验都是不同的。
开发这个app的目的是什么？每个app都需要一个清晰明确的目的。如何定义这个目的，有一部分因素是取决于你觉得的某个可以引起用户使用兴趣的点。
你的app能解决什么问题？每个app只解决一个独立的、明确的问题，而不是试图去解决一堆问题。例如，“设置”应用使得用户可以修改设备的基本设置。这个应用只有一个界面给用户使用，用户通过这个界面完成一系列的设置任务。如果你的应用试图去解决一堆问题的话，那么不如考虑划分多个应用。
你的app有哪些内容? 考虑清楚你的应用需要有哪些内容并且这些内容将如何与用户互动。然后设计将这些内容设计成用户界面呈现给用户。