Twine is a program that you can install on your Mac or PC or run from the cloud.
Twine is available in a variety of ‘flavours’. All these have been written for different purposes. Some are basic and straightforward, some allow a lot of coding. For writers and aritsts I use Harlowe as a mid-range flavour. It has a lot of macros (options) and while it allows coding, it in no way requires it. It has a great interface which will get you started with some stunning texts.
Dynamic hypertext as a focus
Twine heavily encourages you to think of a page as a dynamic interactive space, not just a sequence of prose followed by choices. It encourages you to place links and interactive elements in the midst of prose, not just at the end, and to use them to change the prose in surprising and unusual ways – inserting or removing text in a previously-read paragraph, changing the styling of words, changing just the link itself, and other such effects to reveal new meaning in the text and communicate your story in a manner unique to hypertext. If you would like to explore the storytelling potential of hypertext, Twine offers an endless array of possibilities.