Hi Partheepan,
There are different options available at the item level to create the SC item but it totally depends on the requirement :
a) Free Text : When you have not standard material defined in the system you could used that option.
b) Internal Goods and Services : When you have standard master data maintained for these goods and services.
c) Catalog : When you have any calalog attached to the SC.
d) Limit Shopping Cart : I well explained in the thread :
Its depends what type you are looking for because interface of the SC changes accordingly and then follow-on document will also changes respectively.
Thanks
Ankit Jain