It's a lightning component you can embed on any record page to create a rich-text editor for any text field.
This component only works under Lightning Web Security. If you are not using LWS, you can enable it in Setup -> Session Settings.
CK4SF was created by Amnon Kruvi. Check out my other work: https://github.com/akruvi/salesforce-simple-trigger-framework https://www.isimio.com https://architechclub.com