What is a software application on a network host that acts as an intermediary between the external and internal networks screening all incoming and outgoing traffic?
A network is anything that is connected together. There are Cable TV Networks, Telephone Networks, etc. A computer network is specifically a network that includes computers.
A local application is stored on a computer for use on that computer. A network application is stored on the server/host computer for use on all computers on that network and by all users