While basically the same, there is a subtle difference to understand.
This URL gives more details, with how-to examples, but to summarise...
Safe Mode only loads the core essentials to allow Windows to start and automatically turns off everything else.
Clean Boot is when you manually disable processes and services that get started when Windows boots.
So while the outcome may seem the same, Safe Mode has many more things unavailable than what Clean Boot does.
This URL gives more details, with how-to examples, but to summarise...
Safe Mode only loads the core essentials to allow Windows to start and automatically turns off everything else.
Clean Boot is when you manually disable processes and services that get started when Windows boots.
So while the outcome may seem the same, Safe Mode has many more things unavailable than what Clean Boot does.