I can't help but think you could have googled "ColdFusion request scope" and done some reading. There's plenty of already-written material on this:
- ColdFusion - When to use the “request” scope?
- Scope types
- Request vs Variables - Which is right? (I personally don't agree with Cutter here, but it's an interesting read)
Those were all from the first page of Google results.
it's all very well documented if you just choose to look for it, but the request scope is exposed to all CFML code executed as part of a request (so the mainline code, includes, custom tag code, CFC method code, <cfthread>
code, etc), so if you need a variable available in all those contexts, then one can use the request scope. Contrast this with the variables scope which is only shared between the mainline code and included files, so not accessible within custom tag code, etc.