Don't understand reservations

what exactly is considered a walk up? i want to car camp.

Walk up = can't be reserved in advance. First come first serve on day of camp.

Upper Pines campground in closed at least thru mid April. As per the current Upper Pines Notifications:

"Due to errors with existing reservations, sites in this campground currently appear available as walk-up or first come, first served and are temporarily unavailable for advanced reservations between Feb.14 though May 21. Sites will become available to reserve within their respective open periods as soon as possible. We are working quickly to resolve this issue and apologize for the inconvenience. Sign up at go.nps.gov/campground to receive notice when the sites become available."
"Upper Pines campground is closed until at least mid-April due to damage from extremely heavy snow. We apologize for the inconvenience. Affected reservations will be cancelled and fully refunded. Check back here or sign up at go.nps.gov/campground to be notified when Upper Pines will reopen."

i belong to Yosemite National Park on Facebook, and this is what was posted the other day.

by the way, is there a way to post a photo to resize it here?