smart forms for standard tables

Hi all,

can any tell me the difference in declarations betwwen type and like while declaring in smartforms.

I have an idea but i am little confused and do i need to declare the standard tables because i have my data retrieval in smart form it self.

like if i am retrieving data into internal table from mara,do i need to declare mara because its giving me an error if i don't declare. when i declared mara like mara in global definitions .it worked fine for me.

Thanks in advance