what is `optimistic updates` in front-end development

I'm reading the intro to redux pattern, and there is the following paragraph there:

... consider the new requirements becoming common in front-end product development, such as handling optimistic updates, rendering on the server, fetching data before performing route transitions, and so on.

My question is what is optimistic updates here?

Solution 1:

In an optimistic update the UI behaves as though a change was successfully completed before receiving confirmation from the server that it actually was - it is being optimistic that it will eventually get the confirmation rather than an error. This allows for a more responsive user experience.