Anyone know how this text editing is made? (swiftscribe.ai)

I am planning to develop some frontend interface similar to this example.

http://ift.tt/2BfJDGA

I found out that each text is displayed as elements so they are clickable to trigger actions, also the are with some data binded as attributes, secondly it allows people to directly edit the text, while i am editing the text, it really is deleting and adding elements, may I know how is it done please?

I inspected the website a bit and found out they use knockout.js which i guess is for data binding, I am very curious of how the whole text editing works that it allow user to add and delete the elements just by typing normally. Thanks!