BAPI creation parameters

Hello ,

I am new to BAPI and i m creating a Bussiness object using SWO1 transaction.

Frnds i want to know Practicaly whats the use of the following in SWO1 T-CODE.

1) OBJECT TYPE

2) INTERFACES

3) KEY FIELDS

4) ATTRIBUTES

5) METHODS

6) EVENTS

Frnds i have created a Remote function module also where i am fetching material description using material number.

Here i m calling the function module in API Method.

But i m unable to understand why we first implement , then generate and then release.

Looking for neccesary help.

Thanks all.

Regards,

KAVITA