part body, Boolean operations
It allows you to add, subtract geometries or simply find the intersection between 2 or more geometries.
In short, these commands allow you to add or remove material easily to the main body. And without these commands it is hard to do design.
Booleans are also useful in reducing rebuild times for complex parts.
That means you must use every time when you are designing.
For Making complicated plastic and casting parts...
Boolean Operation is an one of the important part of catia, actully it is not in catia only, it is in cad. So you can find it in all types of cad softwares.
Now come to boolean Operation, It is used to add(combine), subract(remove) or intersect the object.
If you want to add or merge two object you have to use add option but object should be teach each other.
If you want to remove material of a object from other teaching or intersecting object then you should use subtract option.
And the last one is Intersect it is use when you want to remove or save the intersecting part and remaining not want.
Boolean - The name sound familiar. Yes, it's basically derived from boolean algebra. If you know it then it's great, if not just leave it.
Why do we need boolean method of design, when we can use pockets and pad and other simple options. To answer this, just imagine how a bolt is manufactured, we take rod of bigger Dia and then we will perform turning operation to remove material from workpiece. So, you can come late boolean approach with this. We can say boolean is a manufacturing approach.
CATIA V5 has a very powerful and extensive set of solid modeling tools that Boolean Operations are usually not required for most designs. However, they do provide an additional capability for special situations such as molded and cast parts as Zakir stated earlier.
listen my dear friend....the why depends on your prospective idea or view towards tht design so i don't think anyone's answer can satisfy you but when you find some complex geometry design, where you can't use your operations, to get that perfection u want, then use boolean it will satisfy you u will get to know when to use it
Everyone is sharing their experience towards Boolean operation
For example you can make through hole on rectangle plate in many ways
1. Make the pocket
2. Create Hole by hole command
3. by Boolean Operation.
When you make complicated part with have my circuits for cooling, Gas etc, then you will come to know how Boolean operation is necessary for it.
there is no compulsion on design, you can use any command any time depend on the requirement.
There are some Best business practices for design that every industry follow.
I hope this answer will satisfied your answer.