Hi @BHANUKIRANJ,
Form design and Form layout are both tools how to change forms, not only related to ITSM.
If you want to get expertise or more confident, just go any play with it at your PDI.
To start, go to any form that you want to update - e.g. Incident, User, Location, ... and thete click the triple line > Configure and select one of the options:
Then all these tools can do the same thing, just with different way:
I never used Form Builder really because it was introduced after I already got used to the other two.. and when I am supposed to add one or two fields I use the Form Layout (faster) but if it is more fields or creating related tabs or sections, then I go with Form Design
Unless you already have it, go to:
https://developer.servicenow.com/dev.do#! and request your own PDI where you don't need to worry of breaking anything, it's for free and you can always reset to default if something's broken. This is the best way how to get confidence and how to learn things.
