The SAP NW AS can function both as a Web server and as a Web client. In its Web server role, it can accept HTTP requests from any Web client (for example, a browser), process the requests, and send a response back to the client.
In its Web client role, the SAP NetWeaver Application Server creates HTTP requests in an ABAP program, and sends the requests to a Web server. The client then receives the responses and proceeds on the basis of the responses.
In both cases, both stateful (context is maintained) and stateless (context is terminated every time) modes can be used (see Stateful and Stateless BSP Applications).
Choose the links below for more information on SAP NW AS in both server and client roles: