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

2> means "redirect standard-error" to the given file.

/dev/null is the null file. Anything written to it is discarded.

Together they mean "throw away any error messages".