A repeatable repeats or duplicates a group of identically styled elements. Styling refers to how the individual elements are visually formatted - think font color or size.
At its core, a repeatable is a styled list. For example, a speaker listing may contain a center-aligned avatar, the speaker's name in a headline with a green background, and the speaker's title in purple font.
The most common blocks with repeatable functionality include Speaker, Sponsors, List, and Schedule blocks. All of these blocks can be found within the Block Library.
A repeatable empowers the user to add new content, in this case, an additional speaker, without having to style each of those elements a second time. This is because styles only need to be set once on the master repeatable.
Similarly, if the user wanted to change the style of an element, all repeatables can be updated with a single click by opening and editing the Master Card repeatable.
Check out our best practices when it comes to styling a repeatable here: What is the best way to style my repeatable block?