Welcome to the REST Server for working with Hyperledger Fabric.
tl;dr; Given a Hyperledger Fabric infrastructure, you give the rest server a Connection Profile of your organization's 'gateway' Peer; the rest server then stands up a OpenAPIv3 standard REST server allowing access all the way to the transaction functions of the smart contracts. Stand this up next to your 'gateway' peer with a conneciton profile and identity.
Please note that this is an Apache-2.0 project, it is offered without any formal support from IBM or anybody else.
For full details see How to run Starter Server