A forward proxy is a proxy configured to handle requests for a group of clients under the local Administrators control to an unknown or arbitrary group of resources that are outside of their control. Usually the word “forward” is dropped and it is referred to simply as a proxy, this is the case in Microsoft’s topology. A good example is a web proxy appliance which accepts web traffic requests from client machines in the local network and proxies them to servers on the internet. The purpose of a forward proxy is to manage traffic to the client systems
A reverse proxy is a proxy configured to handle requests from a group of remote or arbitrary clients to a group of known resources under the control of the local Administrator. An example of this is a load balancer (a.k.a. F5 LTM/ application delivery controller) that provides application high availability and optimization to workloads like as Microsoft Skype, Exchange and SharePoint. The purpose of a reverse proxy is to manage the server systems.