Targets
A deployment target can be understood as a machine, or a set of machines where the application is going to be deployed.
Ultimately, this machine needs to have some component listening for incoming requests. Generally, a web server is exposed, that will in turn talk to our application internally, e.g. using a UNIX socket.
However, it's also common to see Application servers (like Zend) or even Servlet containers (like Tomcat), that allow you to deploy your application on a fully fledged web server.