The flow of traffic from a reverse proxy is incoming traffic from the internet coming into your company network. The reverse proxy is placed in a boundary network called the Demilitarized Zone (DMZ). It performs the authentication and decryption of a secure session so it can filter the incoming traffic.
Example: If a company sets up a webinar through Skype or another video conference application, they can invite potential customers. All of the conferencing requests will pass through a reverse proxy that authenticates them and redirects their session to the relevant Skype server.