Frame Relay Vs X.25

Hello Friends
I want to know that what Is frame relay
Is it a Service same like that a telephone company provide us in form of ISDN,,or is it a wan protocol
Why do people say that Frame relay works on Leased Lines.
Who Provide this service to us
People says that Frame relay has its own cloud,,,what does it means?
Where are frame relay switches placed.
On routers we encaplsulate it on ISDN or Leased Lines,,,,then how is it better that ISDN in Bandwidth case…..
I am Damn Comfused that what exactly is Frame relay?
Same all these Questions are for ATM….
Kindly give me detail about this
Thank you