Correct way for sending POST method via Rest Json Rest API

If I want to use They declare their HTTP Input as following:

application/json body specifies JSON input data (UTF-8 encoded)
application/text body specifies text input data (UTF-8 encoded)
application/octet-stream body specifies binary input data (raw bytes)

lol funny even Tables are properly shown here :smiley: haha thats true markup!

Example on their Website for a request (JS):

// include the algorithmia.js library

var input = "YOUR_NAME";

      .then(function(output) {

So I should send the Header Parameters as defined? Any example for that?
I guess its similar to other REST JSON Requests as I dont need any token here to make authorization? They write on their page:

API requests are authenticated by a key which can be found and managed from your user profile. With every call to the API, the user must be authenticated. The API has a simple means to do this by passing in your key as an HTTP “Authorization” header with the request.

Could you explain the practical use case for using this algorithmia API?