microCMS is a Japan-made API-based headless CMS.
For more information about headless CMS, please refer to this article.

Getting Started with microCMS

To start using microCMS, first follow the steps below.

1. Account Registration
2. Login
3. Create a Service

After that, you will configure settings within the service and implement it for display.

The easiest way to understand is to retrieve data using JavaScript from the browser, so please try this method first.

We also have a blog post that explains the process from account creation to displaying it in the browser.   
If you want to get an overview, please refer to this as well.