Confusion about function parameters

Hello everyone,

                          I am referring to the functions described here:  

                         Now some of the function descriptions explicitly mention whether a parameter is "IN" 
                         or  "OUT", and some don't!!

                         Am i to understand that when this IS made EXPLICIT, there DO exist "OUT"  parameters 
                         and when it is NOT made EXPLICIT, there DO NOT exist "OUT" parameters ??

                        Also there is the return parameter. Is this always one of the OUT parameters???

                        Then again, in what order (left to right) do we collect and also supply various 

                       Can someone shed light on these matters??

Thanks a lot