Twitter and RSS are the two ways that you can obtain information rather quickly and direct to the device that you are using. Twitter is a microblogging service in which you can follow different personalities, and you are notified whenever one in those you follow puts up a fresh post. RSS is the anacronym for Really Simple Syndication, which means it is not a service, but rather, a standardized format for broadcasting information.
Twitter is a microblogging service, while RSS is a method for information syndication. You need to subscribe to Twitter to use its service, but you need to have your site to use RSS. Twitter is somewhat limited compared to RSS. The popularity and uncomplicatedness of twitter have also spread to other media, making it more embraced by users.