When it is clicked on it will take you to another site. A computer accessory connecting to a telephone line to allow communication between computers. When connected to your ISP's computer it gives you access to the internet. When specifying links you use a path. A path instructs the browser how to get from where you are to where the link is.
Paths are absolute or relative.
Relative links are directions that start from where you are. AOL and CompuServe have many POPs scattered around the nation. Post Office Protocol. This kind of POP is what handles your mail. Your POP account is your email account.