$ ls -l /bin/bash
-rwxr-xr-x    1 root     wheel      430540 Dec 23 18:27 /bin/bash

The rest of the field consists of three character triplets. The first triplet represents permissions for the owner of the file, the second represents permissions for the file's group, and the third represents permissions for all other users:

"rwx"
"r-x"
"r-x"

Above, the r means that reading (looking at the data in the file) is allowed, the w means that writing (modifying the file, as well as deletion) is allowed, and the x means that 'execute' (running the program) is allowed. Putting together all this information, we can see that everyone is able to read the contents of and execute this file, but only the owner (root) is allowed to modify this file in any way. So, while normal users can copy this file, only root is allowed to update it or delete it.