Both CCSK and CISSP are offered by a common certification body, (ISC)2, recognized as the world’s largest non-profit IT Security Organization. Both CCSK and CISSP helps in adding credibility to your profile. Now, coming to the differences between CCSK and CISSP, they both are different fundamentally. CCSK (Certified Cloud Security Knowledge) is a certificate, whereas CISSP (Certified Information Systems Security Professional) is a certification. CISSP could be used for employment opportunities to further advance your career, whereas CCSK could only be used for showing that you have the required knowledge on the topic. With CISSP you need to maintain certainly CDUs (Continuing Development Units) to remain certified as it is valid for 3 years.
If you wish to know more about CISSP and probably want to get certified in CISSP, enrolling in a good CISSP certification course, will help you get certified in CISSP. If you are a complete beginner to this certification, I would suggest you check out the CISSP tutorial.