How to use api update by store.update() ?

Code:

 api: {
                read: 'php/newgrid.php?mytype=list',
                create: 'php/newgrid.php?mytype=add',
                update: 'php/newgrid.php?mytype=edit',
                destroy: 'php/newgrid.php?mytype=remove'
            }

i try to use

store.update()

it can call api update function

but about update()

i don't understand to add option in ()

please help