Captions are special title widget with design styling from the theme. More styling options will be added in the upcoming theme versions.
Captions should be used as section titles, and can be customized in typography, alignment and colors.
Once added to the page, right click and select "Edit caption".
In the text field change the caption text. If changes are not taking effect (Elementor can sometimes be lazy) just change the text.
The caption size can be set in the "Title typography".
Example:
