Hi:
Form scripts and client scripts are the same thing. This will run on the “client” side of the app: the form or list view.
Note that client & server scripts are the proper way to customize existing doctypes (i.e. erpnext customer doctype). You could edit the code (.js and .py files) but this changes will dissapear after updating apps.
When you create a script (client or server script) this will be stored on the database (data), so it will remain even after updating app. To “packing” the scripts into the app, you need export them as fixtures by including on hooks.py file . This way, the scripts will be included when you install the app in another site. Fixtures can be used to export other database data: custom fields, reports, translations, etc …
Take a look here:
Hope this helps.