An Acronym for Rapid Application Development. It usually means an IDE with a point-and-click tool for building graphical user interfaces.

There are at least two schools of thought regarding their use. Depending on which school you follow, RAD tools are…

• …best used for rapid prototyping of an application, as they have high-quality form builders and allow fast development of complex interfaces. However, the code bloat that comes with the abstraction that RAD provides is detrimental to the performance, so they are unsuited for final products.
• …perfectly fine to use for all tasks.

Regardless of your own opinion, be aware that abstractions cannot replace knowledge of how things work. Sure, you can design SQL queries visually, drop a DataBase component onto a form, and have it a grid of values populated automagically. But if you don't understand SQL or how DataBase connections are made, chances are you'll create inefficient and/or too inflexible code and run into problems sooner or later. You might be missing heaps of ways to perform a query, some of which might be better than what you picked, simply because your RAD tool limits your world view and keeps you from educating yourself.

And because the expressive capability of GUIs is inherently limited, you may often find yourself unable to create something that fits a complex spec exactly.