Instagram exists in the desktop version, but one option is currently not possible to publish via PC.
At first, you could only view posts from other users, so Instagram has added over time that you can view stories, comment, and eventually post messages.
It remains to introduce the possibility of publishing from a computer, which they will do soon.
Users will be able to do everything that can be done on the application on the computer, so in the end it will only be necessary to develop a desktop search option, which is great for the application.
Instagram is currently testing the latest feature it is inserting, but it is not yet known when the ability to post will reach our computers.