This feature enables you to update the region preferences for your website. This will make it easier to display dates and times in a format most suited for a given region. You can also change the text direction based on the selected language.
Go to Configuration -> Region.
In the Region tab, select the Language you want your website to be in from the drop-down list.
Pick the Region where these settings will be relevant.
Based on the language you select, the Text direction will be automatically selected. For most of the languages, including English, it will be left to right. For Arabic and a handful of other languages, the right to left option will be enabled.
Select the region's Time zone.
Select your preferred Date format.
Select your preferred Time format.
Click Save.
Choose the required RTL language and Text direction as Right to left. Click Save.
Once published, you will now be able to see the website in the RTL layout.

You can also refer to the images below to see the difference between a regular website and an RTL website layout.
LTR layout:
RTL layout: