This is useful when you want to execute code as an event rather than in the current context. A typical example is when a CAPI callback needs to do something in the current process which is not appropriate to invoke inside the callback.
For the object to actually be processed as an event, the current process must process events sometime after
current-process-send is called. In the "standard" situation, for example in a process started by CAPI, the object will be processed as an event by calling general-handle-event.
LispWorks User Guide and Reference Manual - 20 Sep 2017