What does “/dev/null” mean at the end of shell commands

Question

What is the difference between the following commands?

ssh myhostname \"command1; command2;...commandn;\" 2>/dev/null
ssh myhostname \"command1; command2;         


        

Answer 1

1) Pipe everything on standard error to /dev/null (so ignore it and don't display it)

2) Dev null just points to nowhere, pipe anything to that, and it disappears.