Content type publishing is a feature that will allow you to publish content type to other site collections in SharePoint Online. So you need to create the content type just once and then just publish it so that rest of the site collections can make use of it.
Steps to achieve it:
1. Create a private site collection.
2. Create a content type. ( Do ONLY the first two items in the article)
3. Enable the content type publishing by going to Site Actions -> Site Collection Features -> Activate Content type syndication hub
4. Once activated, Go to Site Actions -> Site Settings, Under Galleries click on Site content types.
5. Click on the content type that you created.
6. You will be shown the below screen. Click on "Manage publishing for this content type".
7. Then you will be given the below screen, choose publish in it.
9. SURPISE!!... You will hit an error....
The error says that there is already a site collection which has content type syndication hub enabled . But we know that we have enabled it in only one site collection.
Thats not true!!... By Default SPO gives us a site collection which is hidden ( not sure why) in which the content type syndication hub is enabled. So next question is, if its hidden, how do we access it??. Follow the below step.
a. If your sharepoint online site is <somename>.sharepoint.com, then you can access the hidden site by appending your site with "/sites/contentTypeHub".
Redo Step1 till 7 in this new hidden site , and Voila... No error!!...The content type is published. The content type synchronization job runs every 15 minutes. So after 15 minutes, you should be able to see the publised content type in other site collections..
I am still looking into why is it a hidden site?? and why cant we have this done in other site collection??.. Once I have the answers, I'll update this blog.