Use cases for web application API?

Question

Nowadays a lot of web applications are providing API for other applications to use.

I am new to the usage of API so I want to understand the use cases for it.

Lets take Basecamp as an example.

What are the use cases for using their API in my web application?

1. For inserting current data in my web application into a newly created Basecamp account instead of inserting everything manually which could take days or weeks if the data is huge?
2. For updating my application data when the user changes something in Basecamp. If so, how do I know for example when a user add/edit/remove a contact in Basecamp. Do I make a request and check every minute from the backend?
3. For making backup of the Basecamp data so I can move it to other applications if necessary?

Are all the above examples good use cases for the usage of API?

Are there more use cases?

I want to have a clear picture of why it's good to use another web service API and how I can leverage that on my application.

Thanks.

Answer 1

APIs are used any time you want to get data to/from an application without using the default interface.
*I'd bet there's a mobile app would use the basecamp api.
*You could use the api to pull information from basecamp into another application (like project manager software or an individual's todo webpage) *the geekiest of us may prefer to update basecamp from a script/command line rather than interrupting our work flow to open a web page and click around.