yes it can be used like that but there are some instant messaging that you do not need to enter in a chat room to be able to use. Like Yahoo Messenger. you just need to have the Yahoo ID of a person...
Chat is usually an open "room" where several people may talk at once in a type of community where as instant messaging is generally from individual to individual, although instant messaging may have...
Emails take several seconds to send and you have to click to view each message whereas instant messaging is instant and has one screen showing both yours and the other persons messages in one as a...