Blu-ray player shows black bars across the top and bottom of the screen

Black bars on the screen means the aspect ratio of your TV is different from the aspect ratio of what you're watching, or basically, the video you're watching is wider than your TV. In order to show the entire video without cutting the left and right edges off, black bars are used at the top and bottom to fill in the extra space on your TV. If you don't mind the sides being cut off, then you can usually adjust your aspect ratio on your TV to reduce or remove the black bars.