"Case Ready To Be Scheduled for An Interview" simply means the U.S. Citizenship and Immigration Services (USCIS) officer reviewing a green card applicant’s case did not find any initial issues with the application. Their chances of getting an RFE (Request for Evidence) are very low right now, which is good news! Their local USCIS office now has the application in their hands.
This does not necessarily mean an interview will happen anytime soon; it can still take months for an applicant to receive their interview date. The status that does signify an interview notice is "Interview is Ready to Be Scheduled." The applicant will receive a notice in the mail one month before the interview.