For a list of all components and their purpose, please refer to this list of components.
When published, a Text block looks like this:
Like the Text and media block, the default editor mode is "Basic HTML" but you can change that to "Full HTML" if you prefer.
Enter the section title and the main body text of the text block in the data entry screen.
There is no individual 'Save' button for a component. Components are saved when you save the page.