>ftp- ftp baiscally needed for file transfer service..probably you have got that some software or mp3 or ... any other types of application can be downloaded from server...over internet or internal network..to transfer file quickly. ftp use file transfer protocol..that perticularly speedy than other file transfer system.
> router- primariry used for interconnecting two or multiple different network, and breaks up broadcast domain.
> firewall- provides security .. and you can add customize security policy for ur network
> gateway- think like..u have a door (interface) to exit out for another room (network), .. sometime also refer to router. gateway can be different types of .. like, voice gateway...payment gateway...etc.
> web- world wide web..all the website .. also .. linuxquistions.org
is hosted on a webserver..
All above can be service of a network. what i can suggest you .. is, go to google and search for "networking" "how internet works" and you will be able to find out lot good stuff to