All rights reserved
Sometimes you will see the phrase "all rights reserved" as part of a copyright notice. For example: "© 2021 Stephen King. All rights reserved."
This means that no one may use your work unless they obtain your permission. This statement is not legally required, and failure to include it has no legal significance. Since others may not use copyrighted works without the copyright holder's permission, the statement is redundant.
If you include the statement "no rights reserved," it means that you are permitting anyone else to use your work. This is occasionally done when the work is being published for some charitable or public-interest purpose, and the creator wants it to be available for general use by others.
Although the phrase "all rights reserved" is not required, there is no harm in adding it. Someone unfamiliar with copyrights may see this phrase and be deterred from copying the work.