If I buy the 2 day one park pass from sams club, can I go the Disneyland one day and California adventure the next day ? Or does it mean I can one go to Disneyland or California adventure for two days? I’m confused

One park per day, meaning one day California adventure and the next day Disneyland classic

If it's labelled as a "park hopper" then that covers both parks. Fine print on the back/bottom should specify, but if it doesn't say "hopper" probably just one park per day

That means you can go to one park each day. You can go to Disneyland on one day and then DCA the next.