What does it mean when my USCIS status says "Case Was Received"?

This is simply the very first status your case gets — it means USCIS has logged your application into their system and assigned it the receipt number you now use to track it.

There's nothing to do at this stage but wait for the next update. It doesn't indicate anything about your eligibility, and it doesn't mean anything has gone wrong if it stays at this status for a while before changing — this can be normal, especially for form types and service centers currently handling high volumes.

The next status people typically see is something indicating biometrics scheduling (if applicable to your form) or a move to active review — both are also normal, expected next steps, not signs of a problem.