A server is used by a host computer for information and services. A client is a program which is used to access a server.
Types of servers used in internet:
Web server: It is used to save and display web pages.
Mail server: It is used for taking care of incoming and outgoing emails. Mail severs include Simple Mail Transfer Protocol (SMTP) servers for sending and receiving emails, Post Office Protocol (POP) and IMAP (Internet Message Access Protocol) for saving emails.
News server: It is used to save and send Usenet newsgroup articles.
FTP server: It us used for saving files. A file can be uploaded to a FTP server and can be downloaded from a FTP server to the local computer by using a FTP client.
IRC server: It is used for internet relay chat for chatting purposes.