Siva,
As you must be aware, there are 2 types of Badi's. Classical and Kernel.
Classical are the old ones which you can see and implement thru SE18. Kernel Badi's belong to the new enhancement frame work. These can be viewed both in SE18 and SE19. The main difference is that Kernel Badi's belong to an enhancement spot but classical badi's are stand alone Badi's.
Calssical Badi's:
1. SE18
2. Called thru cl_exit_handler
Kernel:
1. SE18/SE19
2. Called thru GET badi and CALL Badi.
3. Execution is faster than the classical Badi.
4. Are always assigned to an enhancement spot.
In order to understand the enhancement framework, you need to understand the terms used in
SAP and their hierarchy.
1. Enhancement Spot.
2. Enhancement point/Enhancement Section
3. Enhancement Implementations.
4. Kernel Badi
Spot: is nothing but a container for the points/sections. Assume something like a transport which holds different objects. The objects that the spot hold will be either a point/section/kernel Badi or a combination of these.
Points are the actual enhancements. These can be implicit point or explicit point.
Implicit: are always available in any SAP programs (programs/includes/FMs etc). Right click - enhancement operations - show implicit enhancements. You have to click on the spiral icon to modify these implicit enhancements.
Explicit points are those that are provided by SAP. These are defined by the SAP programmer. Something like a customer exit. The SAP programmer has assigned this to an spot.
Section: Similar to explicit. These are defined by SAP and assigned to a spot. The difference between explicit point and section is that, when you implement a section, the existing code in the section by SAP will be replaced by the customers code. In case of EP, both SAPs and customers code are executed.
Enhancement implementations are the actual implementations that we create inside a point/section.
Refer to the below blog from Thomas in SCN. These explains all these in detail.
Let know if you need more explanations.
Vikram.M