Yes, there's a difference between "pass" and "pass out".
Generally 'pass' by itself means 'give' to one person or many, whereas 'pass out' means 'distribute', or 'hand out' and it is ALWAYS to several people.
So in your example,
'Could you please pass me the salt' = 'Could you please give me the salt'.
'Pass out the cloaks to the people' = 'Distribute/hand out the cloaks to the people (there's more than one)'.