`2>&1` redirects FD2 to the current contents of FD1 (stdout), then `> /dev/null` redirects FD1 to /dev/null. That results in your errors going into stdout, and discarding regular output altogether:

    0: stdin  -> stdin  -> stdin
    1: stdout -> stdout -> /dev/null
    2: stderr -> stdout -> stdout

When you flip the order, `> /dev/null 2>&1` moves FD1 to /dev/null first, and then FD2 to the contents FD1 (/dev/null again), so you discard both errors and standard output:

    0: stdin  -> stdin     -> stdin
    1: stdout -> /dev/null -> /dev/null
    2: stderr -> stderr    -> /dev/null

In your example, `cat file` is unlikely to produce any errors, which is why you're not seeing a difference.